Mastodon, does not operate above the ability of a nation state to block Mastodon.

At the info tech department of a large flagship university recently, (and for reasons that are a bit salacious), there was a need to block mastodon servers on campus and some coming from off campus. It was almost as easy as the flip of a switch to turn it off. If a university can do it on their network, it's a virtual certainty that a nation state can do the same.