Which countries really have the ability to project force in any meaningful way?

USA - well, look like stretched to breaking point by particularly unimpressive enemies.
UK - sort of, but only with help and not for long, or against a powerful foe
India / China / Pakistan / Brazil... - strong local power, no blue water navies to speak of (although China is moving to reverse this)
EU - piss ups and breweries come to mind. Most force is from the UK and France. Add in a few cub scout groups and enough bureaucrats to ensure nothing happens.
Russia - blue water fleet mostly beyond repair. Found that economic weaponry is much better.

So I think that economy / military is the way forward, even though the second is not really relevant. (Although the UK is building some massive aircraft carriers so we can put all our eggs in one basket).

The UN is there to pass some incredibly anaemic pronouncements against countries with no friends in the big league. If the country is really unlucky some 3rd world militias will be given blue hats and immunity from prosecution to go and rape their way through the locals until order has been restored or the funds ran out.