The US government believes that Fable/Mythos is a weapon that needs to be export-controlled, and limited to only US customers. Presumably OpenAI/xAI/Google would face the same constraints, for the same reasons.
OS/foreign models are unaffected - OS because they cannot control who runs them, and foreign because they are not controlled by the US government. We could assume that China will implement the same policy controls, but they see the world differently so might not.
So US AI companies are then limited to the US market, effectively, after about six months (the lag between the current frontier models and the OS models). They have much less incentive to push the envelope to create better models, because the US govt might also ban those completely.
The investor froth around the race to AGI dies, so valuations shrink (the current IPOs may be affected), and presumably the bubble bursts. None of the AI companies can afford to continue building data centres, so that all dies immediately. US GDP drops by ~5% because of that alone.
In a year's time, the US is in a major recession because it gambled so hard on AI. Europe less so, only because it was such a distant follower in that race. China is more-or-less unaffected. The best models are now OS/foreign, and AI is moving forward more slowly, but still moving forward.
Any other scenarios?