France and Germany have already made it clear that they won't send troops no matter what happens with UN resolution. The most the US is likely to get is a weak sanction for the troops already there.

I don't expect that to change no matter who's president.

"Why doesn't the U.N. just kick the U.S. right out?"

Interesting idea. The US's decision to stay out of the League of Nations was part of what killed it. Since the UN is essentially a debate club for rich countries trying to prevent things they don't like from happening (as opposed to trying to accomplish anything), I can't imagine it would make much difference one way or the other.