Civillians in the West are worried about threats that might directly affect them. So Biological / Nuclear and Chemical are all worrying things. Machetes, AKs and so on are not since they happen Over There - with Americans' fetish on shooting each other being the Western anomaly.

Regarding modalities of violence, I think that Tokyo / Dresden firebombings were as horrific as use of the two atom bombs and in both cases the loss of life / general chaos and terror was so high to be almost incomprehensible for me to imagine sitting in front of a laptop in my front room. Ditto the "incident" in Rwanda / Uganda which might have led to the deaths of hundreds of thousands of people but this apparently wasn't an issue for the West. Close to being sticks and stones - knives and cleavers in the main part.

Conflicts have in general terms become less violent but I think that this has more to do with our global economy is now far less "land based" - what is the point of having an Empire and having to suppress all those people when you can get far more money from dominating their markets - and they thank you for this? In essence, killing customers is bad, and outsourcing ownership to a local strong man i one's pocket is much more cost effective. China is trying to take as much sea as they can and control the trade links and view this as far more valuable than trying to stick their flag into (for example) Afghanistan. Better to pay the locals for a mining contract and take what you need.

Nuclear missile reductions was a good thing. Of course, now Russia and perhaps the USA are both in breach of it (and both sides kept enough to sterilise the entire planet for probably tens of metres under the surface).

The UN was a good idea. As was the League of Nations before it. That was scrapped as it didn't work but I imagine they now realise that if we keep scrapping these things until we get one that is actually obeyed we'll be doing it for ever. I do not really see how different countries interpreting UN mandates differently when they get one and have a "coalition of the willing" when they don't. The rules of engagement might have altered, but Von Bismark would fit right in after learning the new phrases.