In reality, Hanlon's razor applies. It's better explained by apathy rather than an evil masterplan. China simply doesn't care about non-Chinese kids, they consider that the American government is responsible for American kids' welfare.
†https://googleprojectzero.blogspot.com/2021/12/a-deep-dive-i...
‡https://www.businesstoday.in/latest/world/story/jack-ma-arre...
Obviously China does care about the Chinese internet, it is heavily censored as we all know. But it is a giant leap from "China censors Chinese-TikTok" to "China is trying to make American kids stupid with dance videos". The corollary is that the people claiming this want China to heavily censor American TikTok so that it is more like Chinese TikTok!
Maybe China isn't doing anything. They just allow a company to deliver exactly what people want and people eagerly lap it all up.
Nothing could be further from the truth. Pornography, anything deemed prurient by the government, anything deemed corrosive to social values, even trivial things like the depiction of zombies and ghosts in media, is strictly controlled by the communist government of China without respect for corporate profits.