I think your question is rhetorical, in which case I agree with the sentiment.

The US absolutely could (and very well might) make Chinese models illegal, possibly open weight models in general, but all that will do is keep them out of the hands of law abiding US citizens.

Law breakers in the US and the entire rest of the world would still have access, and nothing in the US will be any safer. People who think regulation will solve the problem should be embarrassed by their ignorance.

If you are a legally operating company in the US just saying it's banned is enough, the threat of enforcement is enough pressure.

You and I obviously can just use a VPN, but 99% of usage is likely as part of a company.