Tiktok algorithms could be considered a form of editorial position(be it foreign government influenced one, or just the type of content they elevate / not remove), and in this sense it is similar to banning a newspaper(which would obviously be censorship) -- journalists could publish in other newspapers. Therefore banning TikTok absolutely is censorship.

>This isn't like China where the government bans any services they can't control

This is literally like this, and done precisely due to the lack of control due to the illegality of overt/direct speech regulation, and the fears that China would elevate content that isn't in the interest of the US in the broadest sense, but that is still legal according to the 1st amendment. The US Government has tremendously more influence on the local/western platforms, and on people who work there. (There is already an appeals court decision about Biden administration overstepping in communicating with online platforms about what content they don't like). The logic goes "We can't regulate speech like we want to, order what we like and what we don't like, but at least we can remove/censor individual owner-editors that we suspect might harbor some harmful intentions. That means no owners from 'evil' countries". That's about it.