For example one congressman asks if titktok used wifi of users to track them and ceo replies something like "titktok needs wifi to work" which may have you go "oh look dumb congressman" but the congressman was asking about how tiktok scans devices in your wifi and collecte that information for tracking and who knows what else (he clarified as much afterwards).
He was also very dodgy and distanced himsef from bytedance which is a weird thing to do.
Some of the big chinese APT breaches are related to data about people. E.g. OPM hack or equifax credit information. This tells me they want information about americans so they can use it against americans. This means to manipulate social groups but more than that you can target people based on their habits and interesrs and turn them.
Even if they couldn't just order bytedance to do stuff you are a fool if you think hacking a company they have physical proximity to or implanting operatives there is difficult for them.
In other words, I am not concerned about teenagers being tracked or looking at some video but rather being made sympathetic to CCP propaganda and against their own country's interests. And it doesn't have to be brainwashing either, you can pick people based on psychological profiles and give them propaganda or just money and use them as assets like the CIA does except you have young people who will go into military and academia soon. And keep in mind, China doesn't care about the next few months they care about the next few decades.
Based on the reaction in support of tiktok I have seen, I believe if a conflict between China and Taiwan is developing it will become like vietnam with many americans protesting against a war and being anti-military. China will win the war before it even starts because even though they would lose a conventional war, the US cannot fight a war without the support of the people.
In crude terms, you will always have propaganda. The US military needs to win over americans using its own propaganda more than CCP, if anyone is going to brainwash you and turn you into an assett it should be your own government.
And to clarify, I mean no moral superiority here. China does what the US does and will do against Chinese citizens. But the fact if the matter is, China is the biggest enemy of the US right now, not russia or isis or whoever else. They have already succeeded in turning the global south against the US and are carefully watching the Ukraine conflict to time any move for Taiwan to be at the moment the US is most worn out with Ukraine and with whateve chaos the election season might bring. 2024 in my opinion would be the best time to invade Taiwan (Xi basically said that's a too priority for his new term).