So from a purely rights and spying perspective having the app be a US app vs a China app makes little difference to me (not that I'm young enough to be a TikTok user anyway).
As soon as you add 'national security' clauses and hide everything away, you don't really have due process any more. You have two paths. The public one, and the one where it's possible to assert (possibly falsely) that it's a matter of national security.