I have to admit I can not fathom the game theory models that some of you seem to be approaching this problem with. Embrace your cynicism, but play it out all the way. People are greedy. Other people in the world want the money that the United States has. This gives the US leverage and power. The United States does not have all the power, but neither does China; that's just the same error firing in a different direction. There is no scenario where the world just shrugs its shoulders and says "Gee golly, I guess I can't even try to have that American money because the US didn't sign this one treaty and that was the only way that could ever happen".
I'm also not saying everything will necessarily be perfectly peachy, because that's also just the same error firing in a different direction as thinking that it's all catastrophe. It's mostly about fiddling around the margins, not massive binary movements. What will really happen is that some things will be better for the US, some things will be worse, and which one you think dominates will depend upon your values.