Because American tech companies make a lot of money from outside of the US. For instance, 1/4 of all Apple revenues are from Europe, and 1/5 from China and China-claimed territories. Only around 40% are from the Americas (so not even the US exclusively).
Would American tech companies be as successfull without ~half their revenues?
In any case, it doesn't matter, the cat is out of the bag. Nobody sane and non-American would trust American frontier labs, because their models can be yanked at will by whoever is in the White House. It would be suicidal to rely on them for critical business or developer workflows. So your options are to go with Mistral or open source Chinese models, hosted within your environment, with the added benefits of being able to control the costs and being able to fine tune the models to better work for you.