The powers can ask their ISP to block crypto access from their connection. That will make people difficult to use crypto but they will still find other ways. People will never gives up to search for the connection to the crypto especially if they see the benefits of crypto to them.

While countries that see the benefits crypto has to them will not do that. This is because they can use crypto for their own goods so they will not do that. So it will not be easy to terminate crypto access from one country but they can regulate crypto to limit their people use it.

It would be better if the powers use their regulation to control their people rather than to block or terminate crypto. They can also benefits from that and maybe they can have a new source of income from the tax from their people who use crypto.

Regulations.
Alas, if the crypto is to be adopted on a larger scale - it's inevitable it's going to be regulated by those that govern everything. From people to what they use.
But it should be done in a good way - not in a way that would make crypto space as a one-way ticket, as a gov. institution.