Even if the government could block every single way in which you could turn your bitcoin into fiat currencies there is still peer to peer trading done face to face, this is impractical for your everyday transaction but it could be done and you could still convert your bitcoin to fiat that way.
I am not really worried about this because slowly but surely people are beginning to accept bitcoin directly and once this is done regularly there is no amount of regulation that will stop it, so if anything at that point we will wonder why convert bitcoin to fiat at all.
I guess this is what blockchains and bridges worked for if in case you can't be able to convert your btc into fiat. There are so many ways to transfer it into any form of cryptocurrency which you can easily convert it into fiat if it is the main concern but you will be subjected to gas fees which is another concern. But overall I am not totally worried about this because I believe that bitcoin will soon be one of the circulating currency around the world and mass adoption will takes place soon.