Well, if the US was serious about pulling the breaks on AI research they could use export controls of advanced chips on any country they don't trust to align with them on the AI front.
They are already doing that, there are only a few places in the world where you can fab advanced chipsets, and China is assuredly working on that. But from a practical point of view, what stops a research group in China having a server farm in Virginia or Italy or Indonesia? It's not like nuclear weapons simulation where the input data is super secret, they can do 99% of the training on a commercial system.