Cryptocurrencies are one of those cats which have gotten out of the bag, and now it is very difficult for it to be put back in. > Short of that, China could na

Cryptocurrencies are one of those cats which have gotten out of the bag, and now it is very difficult for it to be put back in. > Short of that, China could nationalize the miners and run a 51% attack, driving the price to zero. A hard fork which renders nearly all existing ASIC architecture useless can defeat that attack. It would be a huge cost to China, with all that mining infrastructure go to waste. What China could do better is to disable bitcoin traffic to pass through their firewall, and that would be a better attack, because then it would be chaos in the rest of the world, with really high difficulty level, which would take time to readjust because no new blocks would be mind for a while. Then when difficultly readjust, they open the firewall again, and now you got all these China vs non-China btc transactions to consolidate. This is a big concern of bitcoiners, and there are attempts to figure that out, but it isn't an impossible problem. Keep in mind, Bitcoin isn't the only cryptocurrency, PoW isn't the only consensus algorithm, the current snapshot of the chain isn't immutable. In case of catastrophic disruption, the chain will be forked, that disruption removed, and business will continue. > When major powers decide that bitcoin is not in their interest, they will end the experiment. This is an issue for prisoner's dilemma. Major powers aren't a monolithic entity. The interests of Russia are vastly different from the interests of USA. A LOT of world powers are interested in getting off Dollar as a reserve currency. This alone makes any decision on bitcoin between the world powers far from agreeable.