I think a more likely outcome is nobody filling the hole America leaves behind, and the incentives of a multipolar world are much more brutal then that of a unipolar world, as a result I expect a rise of new nuclear armed states.

I think they are brutal for America in particular, but not so much for the developing world. Happy to be wrong about this.

But I do believe that is why Americans are so frightened of a multipolar world (or really, any world where the US isn't the singular superpower).

No not at all. The vast majority of Americans are uninterested in being world policemen when it means it's mainly American boys (and girls, but mostly boys, let's be real) dying in foreign wars.

The Chinese are not stupid enough to send their kids to die in war, and even if they were, they at least have an excess of young males.

I'm not sure how whatever the vast majority of Americans are interested in has anything to do with my point, but...

> The Chinese are not stupid enough to send their kids to die in war

I see you already understand why China would be a better world leader than America!

Everyone's going to get what they want.