Usa invented the Online psyops/spy game with facebook/google. Now they pissed china beat them at there own game.
Wanting to ban a app/service that basically gives your biggest economic and political enemy direct conact to the local networks/brain of your population is understandable.
I mean those are the reasons why china banned Facebook/Google years ago.
Reality is more complicated tho, cause unless the usa is willing to build a chinese firewall for themself, it will be impossible to keep people from using TikTok via VPN.
If the usa would actually care for its citizen privacy they could just outlaw closed source software.