...good or bad for the US. If/when they lose their grip on top spot, who will lead the way? The EU, China, Russia, Japan...? Everybody wants to be number one but that means somebody has to be number 2, 3...etc.

In a floating market, currencies don't move in a vacuum. They fluctuate in relation other currencies. With the global economies becoming more and competitive and fractured, the result might be that nobody ends up on top for long.

In many ways, the US is, on a whole, much more of a xenophobic society than many outside it's borders think. It's common for the rest of the world to look at the US as an imperialist nation but every time there's trouble, they close in on themselves, put up fences and lock the doors. It's not that much of a stretch to imagine them sitting back and waiting until the dust settles.