There is a lot of selection bias in who comes to the USA to study and work. But also, in china, women don’t drop out of the field all together, but rather tend to move into less technical ones (e.g. PM), and are less likely to get the PhD needed to be a researcher. There are likewise cultural issues that make this hard (e.g. China’s leftover women problem). There has also been a lot less outreach compared to the west because communism was already supposed to have fixed these problems (this is changing of course), while the west has been perversely drawing away a lot of gender diversity at the high end with their current hiring practices.
Perhaps India does a bit better? When I visited Microsoft research Bangalore, it seemed a bit more diverse than Microsoft research Beijing.