Coming from someone who uses neither currently but has used Facebook before, I think it’s more to do with the fact that people are used to Facebook, Google and other companies collecting data. Facebook does a ton of lobbying to tell you just how much they value privacy.
Facebooks data policies are supposed to follow US law. As you already mentioned, I won’t go any further on that. With a foreign country that isn’t exactly super friendly with the US, they could use this same data against citizens. You have no real GDPR, or US privacy laws to protect you if China decides to target a diplomats family or whatever.
For most people, it’s probably not going to affect you either way, but because data is something we really don’t understand the full value of. As an Example, ethnic groups could be targeted and tiktok can be used as a data source.
With the whole Facebook being used to potentially manipulate elections, Tiktok could be as well and the US/other countries have even less they can do to stop it.
But a lot of the hate that you’re seeing on the news is playing into China bad and not really casting light that they are okay with US companies collecting the same data. See: www.theatlantic.com/technology/archive/…/373648/