I’m going to challenge your assertion that you’re not talking about

You can interpret my words how you want and I can't stop you willfully misinterpreting me, but I am telling you explicitly about what I am saying and what I am not saying because I have something specific I want to communicate. When you argue that

I believe each country should get to have a say in what is permissible, and content deemed unacceptable should be blockable by region

In the given context, you are asserting that states have an apparently unconditional moral right to censor, and that this right means third parties have a duty to go along with it and not interfere. I think this is wrong as a general principle, independent of the specific example of Twitter vs Brazil. If the censorship is wrong, then it is ok to fight it.

Now you can argue that some censorship may be harmful because of its impact on society, such as the removal of books from school hampering fair and complete education or banning research texts that expose inconvenient truths.

Ok, but the question is, what can be done about it? Say a country is doing that. A web service defies that government by providing downloads of those books to its citizens. Are they morally bound to not do that? Should international regulations prevent what they are doing? I think no, it is ok and good to do, if the censorship is harmful.