They would need to regulate every ISP in the country to block the protocols, and then go after every website just using those protocols under the hood (and most of these would not be in the USA).

I can't see that ever happening especially because these protocols would have non currency uses as well.

Regulate people using handcranks to power portable transmitters transmitting information at variable frequencies to be received and picked up by those who know of beamforming and antenna design.

Honestly, that sounds like a dream scenario for creation of a new, better, fully distributed internet. This is my favorite timeline.

Including the OpenVPN, HTTPS, SSH, and TOR protocols? (All of which could trivially be used to circumvent such a block.)

ISPs would have to block all crytocurrencies for that to work.

That would work, I guess, but that is a huge step to make and governments aren't currently talking about how they plan in banning all of Bitcoin.