At the same time it must be remembered that until recently the USA and S. Africa had actually been on the same side of the Angolan Civil War, though the US had only provided clandestine support to UNITA/FNLA. The fighting had ended in 1989, and it is probable that the end of the Cold War would radically reshape the geopolitical situation a la Iraq. Also, it must be remembered that as bad as apartheid was, there was no active genocide happening in the same way that there was in the former Yugoslavia. So, unless there is a massive elevation in conflict in S. Africa and the US exhausts all other options, it seems highly unlikely that the US sends bombers to South Africa right off the bat without first arming rebels, etc.