That would work out quite nicely in my opinion, but at that point it wouldn't really matter whether it was the US or any of the other first-world nations controlling the world since they all operate pretty much the same way. (although I do like the US for its combination of science and immorality, but then again, the corporations are way too powerful)
The cultural systems will merge regardless of the governmental divisions; heck, we can even see it happening today. (everyone tries to imitate the US and the western world in general) In the end, instead of a hundred crappy cultures we will have one crappy culture; not much of an improvement, but inevitable.

Although I agree that Bush is quite an idiot, I really doubt he actually makes all the big decisions directly considering his intelligence. It is quite likely that he is simply a figurehead while it is the others in his administration who actually make the decisions by influencing him, since he is too stupid to think for the whole nation alone.
