This is a serious discussion. I mean, after I've seen how bitcoin (and other cryptos as well) got dumped badly after an irrelevant law that makes ICOs illegal. I can only imagine now what would happen If more countries do the same thing and It could get worst by make itself bitcoin illegal. Whether we like to admit it or not, most of people would sell everything they have once its made illegal, some may continue to fight the central banking but the sad reality is that as soon as people start making profits, they will dump it and move on.
For me also yes governments can really stop bitcoins after all because the government can banned bitcpins in their country like china and the other countries. The people in their country are not allowed to access any cryptocurrency so that means in that place no one can use it so the bitcpins can be stopped. And imagine if the united nations agreed to banned the bitcoins in all of the country we do not how how much the power they have but i know that they can stop it if they wanted to.