I think Bitcoin will dead if every country decides to ban Bitcoin permanently. Then, there will be no more people using Bitcoin because they might be arrested in this condition. And bitcoin can also be dead if there are a new cryptocurrency which is more profitable, more advance and can fix most of the bug of bitcoin. In the future, there will be more cryptos qualifying these facors.
I agree with you. That is my worst nightmare for bitcoin to get banned by almost all the major countries or all the countries that has a power and huge effect on most of the smaller countries than them and if they are going to ban bitcoin then the price of bitcoin will just go down and it will become useless since there is no user for bitcoin.
we see now that Chinese rumors banned Bitcoin make the price of Bitcoin down about 45%. I can not imagine if the whole country forbids Bitcoin, really you say it is a nightmare.