It'd be extremely naive to assume that they didn't have a back door, didn't have the ability to 'direct' TikTok to do as they required for pretty much anything, and didn't use it to further whatever their agenda is.
The inverse problem is to think of TT as directly an agent of the CCP, which it is not. TT is a company that wants to make money, that exists in a regime where there is no effective rule of law, meaning the regime can do pretty much as it pleases, when it please, and they do do that, particularly for censorship, content control etc.. But otherwise, the company is left to it's own devices.
Much like if you use Google or FB, you can be assured that the US Gov. will leverage that within the normal constraints of the US, which is to say for local policing warrants and judges, and for narrow issues of national security, well, probably 'anything goes' with respect to non-US citizens, 'almost anything goes' with respect to US citizens, but that ultimately the scope of the more acute stuff will be narrow, and ultimately there will be leakers.
Aka Snowden and Assange sadly get a different form of justice, but at least it's a kind of justice and it's in the public domain. You can speak out against Biden all day long but if you leak sensitive docs, that's probably a line that will get you in trouble.
Finally, we need to start to account for corporate surveillance.