American companies are allowed to operate in China, as long as they follow local regulation. If TikTok behaviour is concerning (it is, like google/facebook/etc are also concerning), then introduce regulations that protect users' privacy and only then ban TikTok.
As the other person said, Pretty sure they actually cant. Last I knew all China Business had to be majority owned by Chinese Citizens or CCP or both.
Americans can invest and have minority ownership in china but can not just "operate" in china like you can in the US as a Foreign company.
Infact this was the regulation trump wanted to impose on ByteDance, they needed an American partner to operate in the US, i.e they were in talks with Oracle before Biden reversed the order
Trade is a 2 way street, if our companies can not compete there, then their companies should not be able to compete here.