Why do you say that Congress is making legislation against its own citizens' wishes? A quick Google search shows that polls suggest that twice as many Americans favour the ban as oppose it.
I'm still trying to figure out what the downside of this legislation is. It doesn't ban any specific content or speech, it just bans a particular company from operating a specific platform in the US. Tiktok is still permitted to operate if it is controlled by a company that isn't directly subject to the CCP. If Xi chooses to not let that happen, that is on him. Xi certainly can't cry foul without massive hypocrisy, given that he has already banned virtually all western social media.