If the prevailing East African genetic superiority logic were true, the top US distance runners should be white versions of East Africans. They should be 5'6"-5'8"; 120lbs; light frame; small calves. Instead, Solinsky is 6'1"; 165, heavier frame, unremarkable calves. In fact, if you look at the big breakthrough no-Africans, you see the opposite of what is supposed to be the big genetic advantage. Mottram and Teg are also 6 footers and Ryan Hall is 5'11". Even guys like Nick Willis and Ritz are a bit on the tall side (5'9").
There are a lot of cultural reasons why the East Africans dominate the distance events. But I think the biggest reason is simply mental. US runners have just taught themselves that the East Africans are superior genetically. Recent breakthrough performances should open the door for more US runners to start believing that they can compete against the East Africans and win.