thijs,

Hedonistic? The philosopy that pleasure is the principal good in life? What would that have to do with U.S. isolationism?
I think you're totally missing the point. If our association with the U.N. has taught us anything, it's that the world wants to isolate us, not the other way around.
Fortunately, or more likely by design, our strength, philosophical base, and values such as freedom and capitalism, don't make us too vulnerable to world opinion.