So everyone seems to roughly agree on the lead time. Talk about a Chekhov's Gun. I wonder if the real point wrt China is part posturing and part securing more Pacific bases (possible in the short-medium term with Australian ports). Also, just selling lots of bombs to Australia (part of the AUKUS deal) - have to find a new military-industrial outlet now that Afghanistan is dry!
It's a medium to long term investment in Australian capabilities; yeah it's not available in the worst case scenario of a war in the 5-10 years but assuming diplomacy can avert conflict that doesn't mean that China isn't a long term threat to Australia. Better to start building capability now rather than waiting for a war to actually start. Also, who knows, perhaps Australia will end up leasing a UK or US nuclear boat once they have port facilities in place that would build the expertise needed for once they have their own boats.

Seeing as the US has already been the largest supplier of weapons and platforms to Australia this isn't a new outlet. As you notice, will take a long time to build capability, first though it means investment and upgrading of infrastructure especially ports so there will be construction, education and so on which will yield benefits in the long term.

I'm going to embed some interesting visual aids and charts from recent Congressional testimony, but first:

If Chinese leadership, for whatever reason, is inexorably on a legitimately-psychotic path of Anschluss at any cost - and there's no pressure particularly forcing military expansion here as a conflict resolution strategy , since as you say their opposition's posture is basically reactive, unlike the case with Germany's or Russia's strategic environments in the 1930s - then the probability of escalation to world war, even nuclear war, skyrockets. And if that's the case then it's simply irresponsible to contest China on this (for argument's sake) ultimate national interest. How could Taiwan be worth it? Bad enough for Taiwan to exist as a free wasteland in a hostilities scenario, let alone the whole region or the whole planet.

In the very easy deterrence scenario, as before, just forward deploy a couple carrier fleets off the east coast of Formosa, offer recognition, park like we parked on Fulda and call it a century. If it's maximally difficult to deter China from invading and bearing heartstopping losses, the price is too high for the coalition and for the world, we could conceivably lose outright; we will need to stand down and pull the defensive perimeter back from Taiwan, maybe even from Vietnam, out to where the Chinese really would be unable to crack open Allied defenses or sustain domestic cohesion if they wanted to. (In this extreme version of events I assume Putin's heir will be begging for permission to join NATO at long last if they aren't an outright Chinese client by then.)
Those are interesting visuals, hull count isn't exactly tonnage though they are adding tonnage at a rate we can't match.

The probability of escalation to nuclear war is extremely worrisome, that's why the US has been trying to get more direct communications at lower levels of government with the Chinese. No one wants a war but escalations can happen very quickly and get very deadly.
How could Taiwan be worth it? Well it is vital in controlling the sea lanes for our two major allies in the region, South Korea and Japan. Taiwan is also crucial in manufacturing of microchips, something the global economy is short of and seeing the PRC gain more control of those industries is not in the interest of the US or EU.

In the deterrence scenario, that's why I've advocated in the past for putting actual US troops on the ground. It the PRC choosing to take Taiwan by force means that US casualties and therefore involvement is a foregone conclusion that changes the calculation immensely. US politicians really aren't brave enough to do so though.
The 'first island chain' is the best line of defense though, with Taiwan as a lynchpin in the absence of US bases in the Philippines anymore. If China takes Taiwan and we choose to actually fight them over their next conquest whatever that is the US and its allies will be in a far worse strategic situation from which to do so. There's a reason Japan took Taiwan from China in the 1890s, it is an absolutely strategic location.

But we just get back into the real reasons why Russia wouldn't really start shit, right? Their economy doesn't have the stamina for a total mobilization, and at any rate Putin and his power base would be wrecked by public unrest and internal rivals. There's simply nothing in it to Putinists' advantage to escalate except in the scenario where Europe and the US capitulate on the spot and promise to never bother Russia about anything ever again, slinking off with their hats behind their tails (unreasonably optimistic). And unlike China, the Russian elite seem perfectly happy to focus their attention on exploiting their feudal subjects for personal profit at home. Russia is the paper Ritsar here, the one great power it really is easy to deter (from strictly military aggression I should say). We probably don't need to speak much more of Russia on this topic, other than to remind ourselves that the US nevertheless is doctrinally-bound to maintain a strategic reserve against hypothetical Russian (or other) opportunism in any confrontation with China.
I whole-heartedly agree. Russia is a short to mid term containment priority. Dissuading any further opportunism by Putin is the only really necessary thing as in the term Russian and Europe need to work together for economic and security reasons.
The US will of course need a reserve in Europe but that's the problem with the overall weak standing of NATO in Europe, there's no one there to really take up the mantle in the absence of the US meaning we need to split our resources between Europe and China. China is the immediate and bigger threat, our resources should be focused there. Especially as the two threats involve totally different mixes of what type of war. Confronting China relies much more on Air and Sea power with a capability to retake any islands that China invades. Deterring Russia requires heavy ground units as well as significant airpower as that's what Russia itself values in power projection.

Maybe something like the Washington Naval Treaty would be available to reassure the CCP and lower the stakes a little (or else we recognize Taiwan and form a defense pact,
The US has been trying to get China on board with arms controls treaties with not much luck. It would be immensely in our interest if arms controls weren't just US-Russia.

I don't know what to predict for Turkey's part, but I doubt it's going to be invading Greece anytime while NATO or the EU exist. What's happening with the new canal?

No one wanted the Azeri-Armenian war to spread, since it was such a limited irredentist grudge match between minor countries, without many excesses. To emphasize what I said in a previous comment, it surely does introduce a new era of limited interstate conflict between small states or even regional powers (Crimea/LDPR was the prologue). Morocco-Algeria and Egypt-Sudan-Ethiopia are plausible cases. I'm not sure if the Ethiopian Civil War counts as an instance of this paradigm.
Perhaps, they are NATO's wildcard. Doing resource exploration in Cypriot waters under the Turkish navy's cover is a good way to lead to conflict.
The new era of limited interstate conflict is what makes it so difficult. It takes a lot of effort to contain a war to just one region. Azeri-Armenia caught Russia off guard and they were left unable to support their Armenian allies without getting Turkey involved leaving them to negotiate a peace that gave territory to Azerbaijan after Armenia's sound defeat.

Within limits. Do we declare war on Russia if it is involved in overthrowing a NATO government? Sure, not like we've even had a shortage of casi belli on that account since 2016. That doesn't entail that NATO is honorbound to throw away its strength in a relentless push toward Moscow. First we ensure that Poland and Romania are secure, then we consider our options wrt Ukraine, then we reduce Kaliningrad, and if the war is still ongoing after a year or more we gradually push into the Baltics until a diplomatic resolution can be found. The linchpin is the mutualized assurances (between allies) and the mutualized costs (between antagonists), not the accumulation itself of overwhelming material advantage (arms race). Obviously European militaries should be minimally functional in their own limits, a notional strength is hardly worth having if it can't be operationalized in practice, but I disagree that there is a justification for significant expansion across many countries.
The US and NATO have in general been very good at trying to keep whatever wars they're in contained to the region in conflict. The Korean war was not expanded to mainland China and it took firing Macarthur to ensure that the limit remained. The Vietnam war never involved invading North Vietnam because that'd be a sure way to get China involved outright. The war in Iraq never expanded into Iran despite their manufacturing and supplying EFPs to the shia militias and the Afghan war never expanded to Pakistan despite it allowing the Taliban to regroup after 2002.
Marching on Moscow or conducting strikes against CCP leadership in Beijing are sure ways to start a nuclear war. All sides have too much to lose in escalation. Seeing as stopping a war from escalating is extremely difficult deterring a war from starting is absolutely vital.

Why would EU citizens believe it's useful for them, or for anyone, to have Europe invest in force projection 10000 miles away? Leave alone that there is no unity on a European foreign policy or consolidated military, but not even the populaces of the UK and France - with extant colonial interests in the Indian Ocean - would hardly see the value in the proposition, one which inherently prescribes deployment of force against sovereign states with unfavorable trade or related policies (where have we heard that one before?).
The EU has several overseas military missions with thousands of troops supporting them, improving logistical capability to support those and other hotspots they intervene with is useful. The lack of a united EU foreign policy is exactly what makes it so impotent, does Poland want to support French interests in West Africa? Does Spain want to defend Romanian interests in Eastern Europe? Does Greece want to get involved in Danish issues in the Arctic?
As for EU citizens believing it useful? Well, that's were a lack of vision for the future is a problem. What do Europeans want their role in the world to be in a fifty years or a century? Do they want to just be an economic zone with limited influence beyond their borders? Can that ensure they can maintain their current standard of living and social values?

Why the heck does Norway need firepower and the will to use it (presumably) against Russian resource exploration? Jesus. I would need a whole lot of convincing for why this is a legitimate postural debate. It feels too much like the proverbial hammer and nail. If it creates dangerous expectations for the US to insist on being able to reach anywhere, Europe of all things doesn't need to approximate such ambitions.
Firepower? Artic coast guard and air patrolling doesn't need to shoot at oil exploration, just shoo way exploration ships when they are in Norwiegen or Danish economic areas. Seeing as for Norway at least oil/natural gas are a large part of the economy and the majority of their exports it is in their interest that the Russia's don't build oil/gas rigs in what don't belong to them, otherwise you end up with a situation like the South China Seas island buildng as no one will risk a war just to eject a small outpost or oilrig.
Norwegian Officials: Russian Arctic Expansion Making Security Landscape ‘Difficult’
https://news.usni.org/2021/03/22/nor...cape-difficult

The Axis of Evil famously counted China client North Korea as a member, which tangentially killed any possibility of sustaining the Agreed Framework on NK nuclearization.
Yeah, that's why I mentioned it. The policy of regime change was a direct threat to Chinese interests.

That's a little unfair in comparison, since the Suez Crisis didn't really change much in geopolitics. France and UK were already consigned to the path if decolonization, and could not plausibly continue to project power as they had in the past; the likes of Suez, and Indochina and Israel before it, just proved it without a doubt for those slow on the uptake. The before-after was a difference in self-image rather than in real capabilities or international relations.

France's separation from NATO was politically inconvenient but I don't know that it reduced the US alliance's - of which France remained a member in practice, they weren't laying down the carpet for Soviet troops - preparedness to fend off any Communist invasion. The Iraq War was more of a strain on Europe's usability for US interests (as neocons saw them), and the War on Terror was clearly a proximate cause of instability throughout the Middle East, even if one thinks of it as an enduringly-unstable region, instability that did directly affect the relations of all the great powers among each other and with the world. I can't deprecate all that for the Suez flash in the pan.
Neither power were consigned to the path of decolonization, hell France was still in the middle of its war to keep Algeria French when it intervened in the Suez. Following Suez the UK's 1957 white paper led to a very real decline in capability which was then followed by their withdrawal from East of the Suez in the 1960s. The US essentially telling it's to biggest allies that it did not have their back on interests that didn't align perfectly with the US changed the entire dynamic of France and the UK in regards to all of their colonies and former colonies in every part of the world.
Yes, France was an associate but the the betrayal at Suez and the departure of France from NATO spurred their development of an independent nuclear capability as relying on the US was deemed insufficient.

Maybe a better comparison for 'true' turning points would be the Cuban Missile Crisis, since that one 'little' incident officially inaugurated the era of Mutually Assured Destruction. In the 1950s, the Soviets still had too few atomic weapons, and moreover no or almost no ICBMs, with which to existentially threaten the US heartland. (Notably for the wider topic of deterrence, MAD was most successful when both the US and USSR acknowledged its potency and agreed to restrict their own deployments and warhead stockpiles. But all those Cold War concords are extinct or about to go extinct...)
It was certainly a turning point too, it was the first time that US citizens felt that the threat of MAD meant them too, not just their allies in Europe or Asia. Especially scary when you consider how close the Cuban crisis came to nuclear war when the soviet submarine B-59 had 2 out of 3 of its key officers voting to launch nuclear torpedoes against the US Navy.