No, the First Amendment doesn’t just prevent the government from imprisoning you for speech… that is a ridiculously narrow perspective and really discredits you on the matter.
The First Amendment, as a trivial example, prevents the government from fining you for speech. It prevents the government from threatening to imprison you for speech. It prevents the government from seizing your assets for speech.
FWIW, I’m not arguing that TikTok shouldn’t be banned. I think it’s a propaganda weapon. However it is far from clear that it can be banned under our Constitution. Especially since the mechanics of that ban require coercing American companies and individuals to limit their freedom of expression.