There are very few truly isolated cultures anymore, and of the ones with any military power or intent, most of them are mutually hated across the globe.
A few countries in the Middle east and North Korea are the only places I can think of that would truly pose a threat of any kind and have a real motive. And even then, they aren't a large scale threat of any kind. People like to assume China is gonna go evil(er) and invade, but they literally have no reason to do so. They rely on the global economy, as does every other modernized/developing country.
I can't think of a reason something on the scale of WW2 would happen anytime soon. Less and less people are following religion each year (slowly but surely), so I don't get that claim of religious extremists doing it. People are also becoming less homogenized, with lots of different philosophies in any given country, thus a militant movement feels less likely to unify in one big violent group.
There's still a lot of violence in our culture and entertainment, but maybe that's to satiate the lack of a 'good war'. If anything, that lets us get our aggression out. I honestly can't imagine what the hell could happen that would pin two or more nations against eachother with those stakes. In the 'first world', we wage war with money, culture, art, sales, influence and science now. It's kind of how we've operated for several decades now.
Something I find interesting however, is that the only culture I can think of that puts a lot of pacifist themes in a decent amount of it's mainstream entertainment is Japan. Yes I know plenty of violent crap still comes from japan, no doubt, but think about the anti-war subtext so many jrgps have, and the themes of Trigun, Ruroni Kenshin and such. That kind of anti-violence work never get's made elsewhere in a large scale.
No one has followed that trend at all. That's...interesting to say the least.
