FWIW, I don't recall the major gripe with Saldana's casting being her nationality. From what I remember, the major gripe was that she didn't look like a person whose ancestors were from a central African country, as Nichelle Nichols did. Saldana actually looked more like she could have been from a northern African country, Ethiopia or Egypt maybe.
So they assumed people in Africa don't migrate to other parts of the continent? BTW Ethopia is not in the North, have such folks even met an Eastern African, they come in all shapes, sizes and looks.
To be fair if Earth is as united and global migration is as normal as moving across town, there is no reason why in a reboot Star Trek, white skinned Kirk McCoy and Scotty could not be African born citizens, brown skinned Uhura be born in Australia and Sulu have an English accent. Chekov can stay Russian lol