I think the difference is that ultimately China (the government, not it's people) is an enemy of the "wester alliance" - "the west", if you will. You can work, and even cooperate, with an enemy to a degree, but you don't let them into your house. It's pretty basic at it's core. TikTok is from a simplistic POV, is at the whims of the Chinese government - much like Facebook/Insta/Snap are to the US government although to a much lesser extent. We don't worry about FB/Insta/Snap because they operate within the "western" jurisdiction and are "trusted" within their domain.

Being rational also requires you take real-life risks into consideration. This would be like saying "why don't you treat your friends the same way you treat the local crackhead when he walks through your store? He's just there to buy essentials" - yes, he may be there to actually buy things, but he's much more likely to do something nefarious than your known friends.