Agreed that there's always a risk that something like this sets a precedent for abuse of power to control information by the US government. And we know that the US gov is not beyond spying on its citizens (Snowden, NSA). However, there are still fairly robust safeguards in place in the US by virtual of the political structure, to make this much less likely to happen. Those same safeguards make it unlikely that while Trump and Elon would almost certainly exercise the degree of control that Xi has if they could, they are prevented from the worst by the structure in place.

The problem in China is that there weren't strong safeguards to prevent a totalitarian control (CCP is supposed to be democratic within itself in that leaders are elected, though it's all restricted to party members, of course), and when Xi came into power he was able, within a few years, to sweep aside all opposition, primarily through "anti-corruption campaigns". So he now has a degree of control and power that would be a wet dream for Trump. (And you should see the level of adulation in the newspapers there.)

Now in the US we have a separate problem, and that is we have a system where unelected people like Elon and Zuckerberg, Murdoch, etc., exercise a tremendous amount of influence over the population through their policies and who are pursuing a marriage between authoritarian politics and big business (by the way, there's a term for this, it's called "fascism"). That is a serious problem -- but it's separate from the TikTok issue and shouldn't be used to discount the dangers of the CCP having control over a highly popular social network in the US.