We are talking about a possible TL in which the King of Portugal stays in Rio de Janeiro, keeping his court there in 1822 in the face of possible rebellion (which gets put down with the help of France). Because the King stays in Rio, Brazil does not break away from Portugal even though the bizarre situation of a European nation with it's capital in what would ordinarily be a colony now exists. So Portugal's overseas territories become Brazil's overseas territory and Southern Africa becomes subject to settlement from Brazil.
Portuguese East African is Mozambique and Portuguese West Africa is Angola.Add all the African colonies population up and they come to much less than the 22 million that is the combined population of Brazil and Portugal. So with this POD a "white" "European" ancestory submergance of Africans might have been feasible beginning in the "60s.