These top 300 times last year were earned by 185 different individuals. I looked up pictures or biographies of anybody whose first or last name sounded less white than, say, "Cameron Quackenbush." (I counted one red-headed guy named De'Sean Turner as half black and half white.) This methodology probably overstates the non-Hispanic white percentage by a point or two by missing people with minority mothers or name-changers.
Here are, roughly the demographics weighted by number of times in the top 300:
Non-Hispanic White 82% East African 9% Spanish Surname 5% Black American 2% American Indian 1% East Asian 0.7% South Asian 0.3%
Clearly, the East Africans are wildly over-represented (just as they are on Olympic medal stands), since they must be well under 1% of the US population. They are as common as all other minorities combined! If you subtract the East Africans out, you get whites at 90%, whereas they make up less than 60% of the teenagers in America today. That's rather interesting for what it might say about willingness to put in enormous amounts of effort. (Cross country requires minimal cost, other than shoes, so it's wide open to the less affluent, as the remarkable success of East Africans in it shows.)
This method of analysis could be unfair to people of West African descent (like most African Americans) because 5000 meters may just be too far for their aerobic capacity. (Here's a graph I made up in 1997 showing that men of West African descent weren't competitive at the world class level in anything longer than 1500 meters).There is, however, a fellow named Mikel Thomas, who looks like a conventional African-American, who had three times in the top 50 last year. (His online signature includes an Ethiopian flag, however, so he might be Ethiopian on his father's side — Michael and Thomas are old Biblical names, and Ethiopia has been Christian for 1700 years. Or he could just like Ethiopian runners.)