I base the following post on the cyclical theory of change (for all those society n culture bunnies who are probably sick of hearing about this, lol).
America, as a society, is dying. They are relying on consumption to keep the economy strong, and are focusing on themselves too much. It is also biting off more than it can chew as far as military commitments go. It has reached the zenith of its powers, and is now slowly, but surely, dying off. Notice how the Aussie dollar is worth more against the US dollar these days?
China, on the other hand, is remarkably similar to what America was about 60 years ago. It's building its power base, the economy is rapidly expanding... and show me a world city that has no Chinatown! The population is huge, and it's emigrating now the communist government is going by the wayside, slowly, as it embraces capitalism and becomes a modernised society. Look out world when China gets angry and starts a war... or starts to get its act together and embrace modernity!