In the comments below a question was asked about the non-European admixture in white Canadians, New Zealanders, and Australians. It was prompted by the fact that low levels of non-European admixture do seem to be found in most whites in the Family Tree DNA database where both parents were born in South Africa (granted, a small sample). My hunch is that these individuals must be Afrikaner, because I have a hard time understanding how else one would detect Khoisan and Southeast Asian ancestry (West African and South Asian ancestry would be easier to explain). So what about other “white dominions,” those realms of the British Empire united by being either dominated or ruled by white people. I actually just looked at the data for Australia, Canada and New Zealand. The sample size for New Zealand was small. But, in these cases those individuals of preponderant European ancestry have no non-European ancestry, by and large. A few Canadians do have some fractions of Native American ancestry. This seems in line with the data on American whites from 23andMe. Only a small minority have non-European ancestry. Afrikaners are somewhat like many Latin American whites, in being visibly white European, but usually carrying some recent non-European ancestry because of the history of their people.
Addendum: Please recall that lack of genetic signal from ancestors 200-300 years back is not uncommon. Most Americans with colonial stock for example can probably trace a line of genealogical descent back to a Native American. But, because of the small fraction most of these genealogical descendants will not exhibit any genomic segments identical by descent with these individuals.