IANAL, but this is my understanding.
Same holds true of your 2nd example, if it required Americans to turn in all the books they owned printed on that paper, for example.
it is not a right to have unlimited access to any and all information.
It is only a constitutional violation (by the gov't) to _prevent_ an american citizen from any speech. It would not be a violation to legislatively ban a company, unless that company was the only place you could make speeches, and thus resulting in the outcome where there's defacto speech repression.
However, such a company ban, if it werent due a violation, would erode the trust in the US financial system. Because if the US decides they can just divest you without you violating any current known laws, it will make foreign investment in the US more difficult.
For that matter, how was it legal to change to digital tv broadcasts? CCP tiktok can absolutely still operate a website that wont be blocked. The medium of delivery isnt protected speech.