I guess I'm having trouble understanding why the US would want to "rule the world." That doesn't fit with our normal vision of things. Self determination has become a principle, and that doesn't fit with "ruling" others. Although the U.S has had imperial/colonial episodes in the past, one of our most redeeming traits has been to rebuild allied countries and defeated enemies rather than to subjugate either. Many might resent us for various reasons, but I hope they can respect our ability not to try to treat them as conquered subjects.
In answer to the question: some places would probably be better for it (autocracies/dictatorships, etc.) but others would be hurt by it. Our govt. is not one that necessarily will plug into other cultures.
And single nation rule of the world is fraught with danger. It represents the "ultimate monopoly." No matter how good the motives, I can't see how it would turn out positively.
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