Well, I’ve never considered any of those countries you posted to not be Hispanic/Latino considering my school taught and tested on those cultures each year in Spanish.
I just recently edited my last post an adcom said it would be “disingenuous” to list African American if you are South African.
And on the common app the questions about twofold. 1) are you Hispanic or Latino (yes/no). 2) regardless of your answer to the prior question how do you identify yourself? (With a bunch of other drop downs you can select)
Also if you selected black/African American on the common app the drop down that appears says which best describes your background (us/African American, Africa, Caribbean, other).
On the commonapp it asks if you are Black or African American. Going by what the census says, white South Africans do not fall under this category. The OP can still put white and select other and specify South African.