That sounds like a reasonable argument to create an age limit for social media.
It also sounds like an argument for parents to step in - every child is different and a parent should be doing the parenting rather than Congress and the White House.
Adults are also quite susceptible to propaganda.
Sure, I'm not arguing that propaganda is ineffective. I'm arguing that people should at least have access to the facts and be allowed to make their own decisions. In this case the important facts are simply that TikTok is a Chinese app and the CCP almost certainly influences them.
When it comes to children that is a different story, but the debate should be whether we enforce an age limit on social media. There is at least precedent (for better or worse) for an age limit on things we think children aren't ready or able to consume.