Yeah, looked this up on world athletics and I think all the athletes under 59 minutes were all African. It's worth noting sub 59 was extremely rare before super shoes, and it seemed for a while the record was stalled at Tadese's 58:23. Some of it is probably cultural and a numbers game, when running is a way out of poverty in your country and not just a way to not get a "real job", there's more incentive to go for it if you have the talent and anyone with world class talent gets discovered. Also the culture of running to school as a kid plus some of them inevitably dope and it's a recipe to churn out high performers.
I'll admit, I was a little shocked though when I looked that up and couldn't find any non Africans under 59. Bigger gap there than I was expecting