It’s certainly only the US, because the alternative would effectively mean binding yourself to US providers, which isn’t attractive for anyone outside the US, in the present world-political climate.

Probably just the US. But the US could do what EU has done with e.g. GDPR, Digital Services Act, USB-C regs, where they force any company trading in their region to follow those regulations for domestic customers.

And basically any AI company has to sell to US companies or consumers. That'd probs be sufficient to force them to use US models.

I doubt Anthropic and OpenAI have enough weight to also make the EU ban open models, it would remain a US thing.