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.
Bitcoin is decentralized, yes, but doesnt mean it cannot be subject to regulation. If the governments see bitcoin as a threat to them, then they can make moves to control it. If countries see bitcoin as national risks especially in financial security of theirs, then they can ban or regulate bitcoin. It is possible right now as we see several countries that banned bitcoin. Governments is not into bitcoin because they are not benefitting from it.