Why do many afro americans claim there ancestors built the Pyramids in Egypt?

I know this is a controversial topic.I am white,my father is from Europe.I have never heard any white person claiming there ancestors built those pyramids.Why do some modern Afro americans claim there ancestors built those pyramids?Modern American blacks ancestors come from countries in West Africa like Congo,Nigeria & Angola.Africa is very big & is a Continent,not a country. All of the people I have meet from Egypt have looked like Middle eastern people.And some look they are from Pakistan,Turkey,cyprus or even Mexican.Also most Algerians i have meet have been white people with red or brown hair & very light skin.I did read in National Geographic that there were black Pharaohs & I do beleave that. But my point is that the Modern American blacks that claim there ancestors were the Ancient Egyptians is like Koreans claiming there ancestors built Angkor Watt in Cambodia.I think they were mostly brown people, not black or white.