There are governments plural which need to agree to stop and historically I can think of freon, leaded gasoline and IAEA and the latter didn't do as good of a job as it was meant to do (but arguably as good of a job as was politically possible)
Also arms control agreements, which reduced the world's nuclear stockpiles by 90%. In principle we could do something similar for GPU farms, since they're not exactly easy to hide.
Indeed. Even supranational coordination should be possible, given that extinction means extinction for everyone, and your excellent examples show the possibility. But then, here we are, and the FT just reported:
> Donald Trump rejects calls from tech bosses for AI slowdown
> President denounces demands for regulation as existential fears over technology move to the centre of US politics
These kinds of situations are incredibly common and where the government stepping in is the solution, but we were cursed to encounter this particular challenge with the most venal administration in history at the helm.