Well, the Third Reich was supposed to last a thousand years. Came in a bit short though. One hundred years? Possibly. But just think back one hundred years.

Assuming a non-catastrophic future (which is pretty optimistic), the differential between the wealth of the USA and other parts of the world can be expected to diminish in time, and ultimately the people and government in that part of the world won't have any more power than any other equivalent region of the world.

And I would assume that that would be what Americans would want to happen - it would definitely be more in keeping with the ideas of the Founding Fathers, as I understand them, rather than getting saddled with holding down some kind of world empire.