[i_have_an_idea]

> few of my close colleagues and collaborators are US born- a very small percentage (maybe 10-20%) [..] If it were a true meritocracy, I guess we would expect ~4-5% of US academics to be US born, given that it's our percentage of the world population

It's unrelated to meritocracy. It's just that a significant portion of the world population lives under conditions that are too poor to be able to develop extraordinarily smart people in significant quantities that are able to compete with other smart people born in rich countries. In other words, if you are poor, have poor access to sanitation and nutritious food, you'll be at a severe disadvantage to develop the skills needed to be a top researcher.