Except the operational headquarters is not in China. LA and Singapore are the operational headquarters of TikTok. I think you are conflating ByteDance and TikTok as the same entity, and that is not the case, and quite on purpose. TikTok is a subsidiary of ByteDance, and from almost all accounts the LA based CEO makes decisions. They are not sending data to China, they are sending it to Singapore. There are alleged cases of ByteDance employees having access, but nothing has been proven (not saying it won’t be, but we can’t operate on speculation). Also, data brokers exist. China can get “all the data from US citizens” outside of TikTok.
I am not sure if you are oversimplifying on purpose, but if not you should probably look closer at the corporate structure of TikTok instead of spreading incorrect info.