In the case of FB, the US government would get that data. In the case of TikTok, it's the Chinese government who would get the data on you, the US citizen.
Objectively speaking, it would be strictly worse if lots of data on US citizens would end up in the hands of the Chinese government, because it's a foreign government and, as we know, information is power. Data on one person is not that useful, data on millions of US citizens, even when noisy, can be extremely powerful.
We also know at this point that a feature like News Feed can be trivially used to influence what information people see and how that information is presented, which then influences the people's opinion of matters in the world, even if the information is delivered via a fun, engaging or funny medium, it's still being absorbed by the brain and the end result is the same: successful control of the information dispersed to the masses.
It's one thing for the US government to influence its citizens opinion (all governments do this for various reasons, for example to cultivate feelings of patriotism and national pride), and it's a completely different ball game if the Chinese government can influence what US citizens think of certain matters. For example, they can try to sway the public opinion towards a political candidate that is more favorable for the foreign government, thereby meddling in a foreign election, only this time it's done with a ton of plausible deniability and the foreign citizens themselves are helping out.
This doesn't mean that Facebook is good, just that it is the lesser of two evils, and, in my opinion, it's a strategic mistake on the US's part to allow TikTok to be used en masse by US citizens. I would have banned it a long time ago.
You could also replace US and China with any other two states that can control what information billions of people see on a daily basis and I would argue the same point.