I'm not quite sure what the threat model is that you're suggesting. Are you imagining that a government will demand that browsers drop support for unencrypted HTTP? It would be simpler for that government to just demand that ISPs drop traffic on port 80 (or do deep packet inspection for a slightly more sophisticated approach).
But in any case, what's the danger with that? Are you worried that a government could tell all CAs not to issue certificates to "subversive" websites? Obviously there are jurisdictional problems with ordering CAs in foreign countries not to issue certificates, but I suppose a government could instead require that all browsers (within their jurisdiction) only trust certs from the government-run CA.
Those would certainly be bad outcomes, but if your threat model includes "the government controls what your browser can do" then I don't see how the situation is any worse due to widespread adoption of HTTPS. If the government is going to interfere with your browsing, then it's actually some consolation that other random attackers aren't also able to do that.
The only extra attack I can think of that mandatory TLS makes possible, is that this government which controls its citizens' browsers in this way could then put pressure on Let's Encrypt (via the US government?) to require ID information from all their users (and a similar rule for other CAs, which wouldn't be too hard as most of them require non-anonymous financial transactions). That still seems like a lot of unnecessary work for little benefit, though, surveilling web publishers when this government already controls its citizens' browsers.
But in any case, what's the danger with that? Are you worried that a government could tell all CAs not to issue certificates to "subversive" websites? Obviously there are jurisdictional problems with ordering CAs in foreign countries not to issue certificates, but I suppose a government could instead require that all browsers (within their jurisdiction) only trust certs from the government-run CA.
Those would certainly be bad outcomes, but if your threat model includes "the government controls what your browser can do" then I don't see how the situation is any worse due to widespread adoption of HTTPS. If the government is going to interfere with your browsing, then it's actually some consolation that other random attackers aren't also able to do that.
The only extra attack I can think of that mandatory TLS makes possible, is that this government which controls its citizens' browsers in this way could then put pressure on Let's Encrypt (via the US government?) to require ID information from all their users (and a similar rule for other CAs, which wouldn't be too hard as most of them require non-anonymous financial transactions). That still seems like a lot of unnecessary work for little benefit, though, surveilling web publishers when this government already controls its citizens' browsers.