For humanity to survive one global culture must eventually grow to control everything.
One of the biggest problems I see with China is their racism.
I do not think that economics will prevent another world war. People have oftentimes felt this way, going back as far as Rome. Not to mention the fact that there are only so many resources on the planet and that if we want to survive as a species someone has to basically get control of them all to use them efficiently to get OFF the planet so we can obtain resources from elsewhere and achieve more living space.
If things remain at the current state they are now, we're going to deplete the planet with our exploding population, and wind up killing each other over the scraps anyway.
No lasting peace can be achieved with differant cultures and nations.... One world goverment is nessicary, and really I think only American principles of freedom and tolerance can work on that level. Nobody (including our system) will EVER create a untopia, I just think it would be better than any other option to exist.
China is currently building up their military as well as their economy which is one of the reasons why I personally see them as a threat. Right now they are just an economic power, but that will not last. People should become increasingly worried about how China is sealing itself to outside ideas, while building it's military, and rattling it's sabers.
If nuclear ICBMS become obselete due to some new technology... well... let's just say that if China isn't planning something they at least plan to be ready to conquer the world or make a huge bid for it during any evelope that exists.
A few truely frightening theories (which admittedly have their problems) involve The Chinese Space Program getting off the ground, the Chinese arming their shuttles in defiance of treaties and pretty much going on a global satellite duck hunt to knock out all the communications and military satellites other nations use.
Pretty much the US is the only nation that could do something like this right now, but we won't because we're nice guys. The Russians had the potential but were always balanced by us. Given our current laid back attitudes due to the space race being "over" and seeing the only real point in it all being to place and maintain satellites, and do research, we could be caught with our pants down if China just decides to go out and do it without any preemptive posturing. We certainly aren't responding to the Chinese Space program anything like the Russian one.
At any rate, let's say China does this. Sure, we've still got a bunch of perfectly deadly warheads out there on Submarines that we can use, but ooops our dependance on satellite technology means all of our communications are down and only China has it for the moment. Our automated missle systems can't fire, because they are now blind.
China lets loose with their payload while the western world is going "WTF" to take out some strategic targets, and then usese the military they are building now to swamp the rest of the world conventionally. Unlike other nations they DO have the abillity to put that many boots on the ground.
Basically, when we eventually recover and establish a new chain of command (chances are places like Washington and London are now radioactive craters, quite possibly literally hit by Chinese warheads fired from orbit) we're not only hugely outnumebred with tenative communications, but facing things like those lovely "Yuan Class" submarines that were able to "Tag" the Kitty Hawke (American Carrier) which are going to be out there playing with our submarines.
Okay, this is one of many potential "Red Dragon Rising" scenarios, you'll find plenty of other equally plausaible ones (with equal numbers of flaws) out there, but the fact remains that in ignoring China because the problem is too big, is ridiculous. It's also equally ridiculous to assume it could never happen. Especially given the way China is sealing itself off informationally and some of the disturbing rhetoric that we DO hear leaking through from their end.
See, the whole logic of someone needing someone else to buy their goods is entirely dependant on the existance of two parties, and the fact that one of them can't just come in and take everything the other one has. It depends on a balance of power.
Rome had this kind of an issue, they felt they were too important due to all of their trade, manufacturing, and doing things like maintaining roads, for anyone to ever do anything to them. The decline took a long time, but even in the end you had cities falling while the Romans couldn't believe it because they were (in their own minds) too badly needed by those doing the conquering.
This is where the statement "Barbarians At The Gates" comes from. The analogy being to Romans assuming the conquering horde outside is just there to talk or trade and refusing to do anything even as the threat manifests quite obviously. From the Barbarian's perspective, why bother to trade with the Romans when you can just walk into the city, take everything you want, and lead all their craftsmen away in chains?
Ironically European civilization rose from the ashes of Rome just that way (though that is a great simplification).
The point is that it's foolish to think that things have changed that much.