If all countries shut down exchange trading like China, I am sorry to say not only BTC, but the whole crypto industry would be most likely wiped out.
i agree, but we can both agree it would be damned near impossible for something like this to actually happen. some govs would be incentivized to allow it, if just to soak up a huge financial market that the others are ignoring. but from a financial theory standpoint, liquidity would completely dry up, at least as we know it. a few things would happen, practically;
price would drop, but then rise as people that actually conduct business in btc remain
peer to peer exchange would become the norm, but there would still be dexs that folks would use, as well as "black market" exchanges.
people would actually spend bitcoin on goods and services, and not just purchase it to speculate. price would stabilize, and the volatility would go away after the initial shitshow, and
people would stop mining immediately; the network difficulty would plummet, and it would be profitable for a time for the little guy to mine (the big guys wouldnt stop mining unless the price becomes unfathomably low). this would cycle, like it always does, before we found the new 'level'.