US wealth distribution is much flatter than European. The GDP/capita ratio between Mississippi and Connecticut is less than 1:2, while for Germany to Hungary it's more like 1:4.
China is... China. You can't call yourself the Communist Party and run the global financial system. The world can only tolerate so much contradiction.
The open question now is whether the dollar can be dethroned by nothing: can a basket of currencies become the default reserve?
My guess is the world can tolerate it as long as everybody is making money off it. When that stops, the contradiction might seem intolerable.
The world needs a default reserve that's not tied to any single central bank. For all the upsides there are also real downsides for the US having its currency as the default reserve.
Perhaps, but you could as easily make the argument that the interior subsidizes the stomachs of the coasts. That seems more like a symbiotic relationship than the parasitic one you seem to be implying.
Europe's problems are not unlike the U.S. internal problems where the tech and financial centers mainly on the coasts subsidize the rest of the country. The difference of course is that the states of the EU can exit, where the American states cannot. I'm not sure which situation is preferable.
China is a black box, but so far recent history has indicated the populace will go along with a lot of pain to avoid chaos.