Most of the world's currency is backed by the currency they print? The USA has to spend a few cents to gain a hundred dollar bill, but any other country has to exchange a hundred dollars of actual goods and services (to the USA!). Losing this privilege would be devastating.
The economic power of the US is also largely due to its reputation for rule of law (https://www.youtube.com/watch?v=o5zaImTF92g) when contrasted with other regimes like the CCP. Once that image goes out the window, it becomes no more attractive to foreign investment than any other banana republic run by thugs.
