Just a hypothesis: the fact that there's no need for an American firewall might be a consequence of the information controls being enacted at the level of platform moderation, or DNS resolution.
(I agree with you about authoritarianism in a political sense, but I'm trying to look at the informational "water" in which we're swimming in).
The mistake is in thinking that there is no need for an American (or Canadian, or EU) firewall. The reality is that either due to corruption or naivety, western countries let foreign information attacks and foreign propaganda spreads completely unchecked.
One could argue in the US that this was very useful to the new regime gaining popularity.
(I agree with you about authoritarianism in a political sense, but I'm trying to look at the informational "water" in which we're swimming in).