Speaking of possible Sino-American enmity, one good way to ensure that 21st century geopolitics is dominated by conflict between the United States and China would be to listen to listen to Ivo Daalder and Robert Kagan about legitimacy (via Brian Beutler):
The traditional answer, the U.N. Security Council, no longer suffices, if it ever did. Under the United Nations Charter, states are prohibited from using force except in cases of self-defense or when explicitly authorized by the Security Council. But this presupposes that the members of the Security Council can agree on the threat and the appropriate response. From Rwanda to Kosovo to Darfur, however, and from Iraq to North Korea to Iran, the Security Council has not been able to agree and has failed to act decisively. Its permanent members are deeply divided by conflicting interests as well as by clashing beliefs about the nature of sovereignty and the right of the international community to intervene in the internal affairs of nations.
If not the Security Council, then who? The answer is the world's democracies, the United States and its democratic partners in Europe and Asia. As the war in Kosovo showed, democracies can agree and act effectively even when major non-democracies, such as Russia and China, do not. Because they share a common view of what constitutes a just order within states, they tend to agree on when the international community has an obligation to intervene. Shared principles provide the foundation for legitimacy.
What is a patriotic Chinese defense official supposed to make of the idea that the United States claims that it and its key allies should be permitted to invade any country anywhere without China's agreement while China, presumably, can only intervene with the approval of UNSC P-5 members like the US, France, and England? It would be one thing to try to read the Kosovo precedent as saying that NATO won't give China a veto over actions in its own backyard.
But to survey the wreckage in Iraq, and conclude that despite the lessons seen there we can't defer to the UN (even with an exception for self defense) on the grounds that the UN might sometimes say no is very weak tea. Meanwhile, for all this talk of an alliance of democracies, I see no particular sign that India, South Africa, Brazil, etc., are actually clamoring for a more interventionist United States or Russia's marginalization on the world stage. I don't say we should give China and absolute veto over US policy, but if we don't want China to become an enemy we need the international rules of the road to be something a responsible Chinese leader could possibly accept. Two-tiered sovereignty that classes China among the disfavored nations isn't going to cut it.