> For that analogy to hold, I would need something equivalent to a US visa to post this comment that you are currently reading.

Only if the US required it.

A country you're not a citizen of preventing you from coming in isn't the same thing as a country you are a citizen of preventing you from leaving.

Consider it like this: Suppose you're in Europe and you want to communicate with someone in the US. You could do it in person by you going there, or by them coming to you, or both of you going to some third place to meet. Your country could prevent them from coming to you but not either of the other ones, and you can communicate with them if you can do any of the three. The internet only makes it more efficient.