What? hubris.
When? Soon. (well, not tomorrow or next year, but relative-to-history-soon)
Elaboration:
We're too freakin' obsessed with making sure the entire rest of the world is under our finger. If the USA was the rest of the world's girlfriend, we'd have been dumped a LONG time ago
Yet at the same time we've got so many things going for us. It'd take a real whooping to put us under--other countries aren't quite powerful enough in various areas of development to really make an impact--which is why I think it's going to be us destroying ourselves. We're the only ones capable of it. (and no, I'm not proposing that we'll break out in civil war again or anything like that; military isn't the only thing that brings down empires)