Everytime somebody has tried to argue that to me, it turns out that they believe that there are racial differences that are not based on evidence.
For example, I once had somebody say that the racial outcome differences were not like socioeconomic upbringing differences in outcome, and that though socioeconomic outcome differences were evidence of difference in opportunity, that racial differences were genetic, which is clearly abiological.
So if you are not positing racial differences in opportunity, what are you positing as the explanatory variable?
I don't know what is the primary cause of disparities but i wouldn't assume it's all socioeconomics without evidence.
Maybe different groups are valuing things differently? For example, an Indian may try to migrate to US using PHD as a gateway. So they may be more willing to sacrifice and work hard. Or maybe for some groups PHD (or education in general) brings more prestige compared to others.
There's also ample evidence of racial discrimination resulting in differences of opportunity, in all fields of science. But people are quick to assume that it doesn't exist, or are quick to point out any chance that it may even exist.
This doesn't mean universities doesn't present equal opportunity.
The reason someone is not as capable may be just bad luck (bad parents etc.). But still, society should give positions to most capable ones.
And I agree that we should fix the systemic racism that causes unequal opportunity starting from early in in life.
And if we are to believe the stories that come from Black people that attempt degrees in CS, or STEM in general, they also face significant differences in opportunity at the university level as well. I'm inclined to believe these stories, as everytime I have spent some time investigating they have been true.
Getting PHD is grueling low paid work with insane hours and very distant payoff. You become phd if you are idealist or have nothing better to do. It is possible that with all of diversity initiatives in big tech some potential phd get siphoned off after college - at least FAANG offer livable wage compared to the 30K phd stipend.
There is infinite number of lines that go through a single data point.
What is the population of the world versus the population of the US?
The real reason why the stats are so skewed towards foreigners is that the basic trade of the PhD is a lot more favorable if you don't have the alternative of just taking your bachelor's and going to work in the U.S.
For grad students, the tuition waiver costs the same amount regardless of where the student is from. Assuming you could fill the ranks with (presumably less qualified overall) U.S. students, and the same amount of grant money was available, it doesn't make any difference.
On the other hand, if you are a foreigner, it's pretty hard to break into the U.S. IT job market. H1Bs are scarce. If you can get accepted into a U.S. PhD program though, you get a well recognized credential, and you get a year of OPT and it's easier to get an H1B after that (or at least it was -- I know a lot of this is changing). You also get six years to improve your English. Even if you return to your home country, the U.S. PhD is likely to open many doors.