[slowmovintarget]

Because the law bans the operation of software by a foreign adversary. It does not ban speech.

Legal precedent holds that source code (the expressive part of software) is speech, but that executing software (the functional part) is not speech. Even when the operation conveys speech, the ban is on the functional operation of the software, so the First Amendment doesn't apply.

[AJ007]

It seems like everyone missed the analogy of TikTok being like a Soviet newspaper, but the better analogy was like Tiktok being a tracking device, which transmitted your exact location, along with a microphone and video camera provided by the Soviet. The hardware may be Apple (made in China, designed in California), but the software extends the hardware usage to the software provider. I'm not sure there was any era of US history which the law would have permitted that.