The first amendment doesn't apply to companies. Shutting down TikTok doesn't prevent you from exercising free speech. That's not how it works. Like, I'm not going to bother with this conversation if this is the direction you're going to take it.
And the fact that "Instagram, Youtube, etc." will just do it shows that regulations and laws are required. Systems that prevent companies from doing whatever they want in controlling the opinions of citizens in other countries. How is that compatible with the first amendment? Do you even understand the issue? Do you even understand the first amendment?