This is a US policy for US citizens. Of course they are protecting their own. China does the same. No Facebook or Google allowed in China.
Banning TikTok only treats the symptom , the real disease is that people are way to susceptible to propaganda and misinformation.
Personally I think all closed source social media should be outlawed and all algorithms used should be audited by a third party.
If you've had better luck, let me know (actually).
As for "being China", every country has protections on what goes in or out of the country including media. A lot of countries won't let you own a newspaper or news broadcast channel, so this is the next extension of that sort of idea.
It's the same idea as not allowing a company from the USSR to run a news channel during the Cold War, although obviously the lines are fuzzier and still being discovered with apps and algorithms.