Imagine if all of the US citizens and US Companies all sold all Bitcoin in 2 weeks and did not buy back in,
Bitcoin will be back at $50 and the miners will end up shutting down as they can't maintain the network now because of their excessive energy waste.
Hardly, you are giving too much weight to American holders. It is known that in this world the most holders live in China. If all Americans sold their Bitcoin, it would temporarily go down as you say, but never nowhere near $50. I doubt an American dump is able to manipulate the price beyond a few thousand.
If Trump does the same to Bitcoin, the net would route around it, exactly as designed. We are here in this very forum telling people in India how things would work in that case, USA is no different, same thing would apply: Use Tor, and be proud its an US Navy project, God Bless America.