I think you're confusing ethnicity with nationality. And I'm not, im simply stating what the government and state institutions deem minorities. Only black and Arab African Americans are minority here, not of Afrikaner lineage. Just as a DBE of Asian lineage, can't be a White Russian, but of East Asian decent.
African or Asian is not a nationality its an ethnicity which by definition can be based on national, geographical, or cultural commonality.
http://www.merriam-webster.com/dictionary/african-americanan American who has African and especially black African ancestors
Are you an African or Arab American?