"the Act, as construed and applied, is unconstitutional, since it imposes on the addressee an affirmative obligation which amounts to an unconstitutional limitation of his rights under the First Amendment."
That seems like a very different case since it imposed different rules depending on the content of the speech. The analogous situation to the tiktok ban would be shutting down the postal service, which would be surprising but presumably constitutional.
https://en.wikipedia.org/wiki/Lamont_v._Postmaster_General