The US isn't just a land. It isn't even just an economy or a currency. Most fundamentally, it's a set of rules that limit the power of government, and thereby allow more freedom for people. Everything flows from that, even the reserve currency. (Why put your foreign currency holdings in a currency where the government can arbitrarily decide to change the value? This is why the renminbi isn't catching on, despite China's power.)

That limited government is looking shaky right now. It's mostly Trump, but it's not just Trump - Congress has been increasingly worthless over the last couple of decades, and so the President has to rule more and more by executive decree. But Trump is pushing the boundaries of what the Constitution allows the government to do far harder than any President that I remember, even Nixon.

And if we lose the limited government, then within a generation or two, we're going to lose the rest. It won't be immediate (unless you fall afoul of the government), but it will come.