Facebook is the short game and is taking steps to get better (banning qnon and political ads etc) in the long game TikTok has CP issues that could leave an entire generation open to blackmail from a foreign power in ways we cant even imagine yet. When they address the issue it seems to be in the future sense when the users today are running for office or becoming CEOs.National security takes on many more aspects than where data is stored. It's been proven multiple times that social media companies have been leveraged by foreign powers to influence elections and US policy. If we are really talking about clear and present national security threats, FB is number one right now. Knowing that 12 year old Suzy enjoys dog videos is pretty far down the threat list.
I say this as someone whos SF-86 is in Chinese hands they know my entire history and it is disturbing thing in the back of my mind. I wouldn't want another generation to have to deal with this.