They must delete the entire internet system so that they can "kill" crypto. That's a good thing about decentralization. Even the government will not be able to control it. The best they can do is to regulate certain regulations or laws on this system.
If gov's will want to kill crypto it will be made other methods. In cryptocurrency today exist a big problem - nowhere to pay. And if gov's will stop this way (cash to crypto and back) then it'll be like death