I think the Africa thing is overblown. Not trying to denigrate their heritage but, Usman came to the U.S. at age 8. Israel went to NZ at age 10. Francis, however, didn't move to France until age 26. That being said, he doesn't even have a title defense yet.
There are some promising prospects that have actually lived on the continent most or all of their lives, though.
With the Russians (or nearby countries), they seem to stay in their homelands. Maybe because there is more training opportunities because of Sambo? I don't know.
Now, imagine we get a Chinese Khabib? Imagine what that would do to the MMA world if the population of China became more invested in MMA training.