What are you talking about?? Fiat will always exist, people will be paid in fiat, there'll be fiat using Bitcoin as collateral, governments needs something they can control, just use your fiat to buy Bitcoin from someone wanting to buy fiat for whatever reason. If you think Bitcoin is useless, HFSP, i won't try to convince otherwise, do your research, don't trust, verify. 

 What good is crypto if you cant exchange it for fiat? Nobody will continue to buy bitcoin or whatever if a country screws up exchanges and they disappear....because there is no point , they cant use it