It's simple, the US government will put any Chinese open model companies on the entity list which blocks any company which does business with the US from also doing business with the Chinese companies. This creates a chilling effect where even if it may be harder to tell, no US company will be able to provide or use any overt Chinese open model and won't even risk trying to go around as the punishments for trying to evade the ban are severe.
Hosting and providing Chinese models wouldn't be the same as doing business with the sanctioned entities though, you don't interact with them in any capacity if you only use the weights and don't sign any contracts.
But that's just the thing with open weights: you're not doing any business with company that made the model. They might publish the weights to a, say, European host, and then you download the model from Europe and and run it on your servers in America, and suddenly it's very hard to tell where the model was originally created.