Here's a hint! It's your military. To put it bluntly, European nations and other US allies pretend the dollar has actual value and the US in turn guarantees security and backs the world order based on the rule of law.
Looks like the US is looking to pull out of its end of the deal. That's fair enough, being the world's policeman is sure a heavy burden to carry. I just don't see many people recognizing the implications for the US economy.