It would be much harder to do this in the US because of the First Amendment enshrined right to assembly.

I mean, the CDC can try, but there will be an immediate stay on the rule by some court or another, and the Supreme Court is EXTREMELY unlikely to lift that stay, unless we're in an absolute apocalyptic crisis.

* upon further research, the main support for freedom of travel is under the Privileges and Immunities Clause https://en.wikipedia.org/wiki/Freedom_of_movement_under_Unit..., but doesn't really matter, it's precedent either way.