I think it will not technically be a ban, but a de facto one.
Some variation on, "Open weight models must be A) trained in the USA B) have a public training dataset + training pipeline C) be reviewed by a government 'safety council', etc" Something which technically leaves a crack open for someone to release a less capable model than the commercial ones.
That kind of policy will hold a country back, and why I don't think it will happen. There are already many companies already using Chinese models.
Another confounding factor, if a US company fine-tunes a Chinese model, or vice versa, what is that country that should be assigned to that model.
You also have to consider the competition between the US and China. If the US did something like this, the world will move to Chinese hardware and Ai. The think tanks that talk with legislators understand this.
NVIDIA won't be too happy about that; alongside Micron, etc.
US commercial interest =/= OpenAI and Anthropic.