Apps are a Service and services have been and are regulated for decades now and the system have been always arbitrary as fuck.
In the case of TikTok, the west, as a military alliance, should be concerned due to the nature of current valid Chinese laws and the implications of it.
And e.g. facebook has proven that they don't like to stick to rules about how to handle data. In case of TikTok, this could easily have bigger implications for e.g. the American military.