That's why China is fighting them on this, short of military intervention we can't absolutely prevent US from censoring tiktok, but we can make it hurt their reputation so much that US gets deterred every time they consider it.
TikTok being ban in the United State can also be seen as a win for China. 150 million American will inch closer to believing their government is corrupt and they also live under authoritarian/oligarch rule. There are now 2 billion Tik Tok users in the world, Americans not creating content on the platform means US loses soft power exposure. If i was bytedance/china, i would auto repost some of the good douyin content over to tiktok to push Chinese softpower.