China has tried to ban Crypto currency about 4 or 5 times and has failed every single time. Its basically impossible to ban it. You’d have to shut down the entire internet.
One of the biggest exchanges is KuCoin. That is extremely decentralized and is owned by no one. There is nobody for the US to sanction or arrest. There are no servers in the US to shut down. KuCoin requires no KYC (Know Your Customer....ie identification). Anybody can trade there. The same is true of other decentralized exchanges. They can’t be shut down by any national authority either. Anybody can buy and sell and trade crypto on those decentralized exchanges.