Oh, there's no shortage of insanity out there. Ethnic cleansing is horrifying and all too common, and despite a universally accepted declaration against genocide, as a world community we seem to just watch it happen ... over and over and over ... unless there are natural resources or strategic partnerships in the offing of course.
I don't want to get into a debate about which is worse, because both are equally terrible, but they are two very different things. What's happening in the countries you mention, what happened before - that is and was genocide.
Where ethnic cleansing is brutally ... direct though, apartheid has a way of sneaking through the back door as being "for their own good" or "self-defence" or whatever. And because of that it's easy to miss and even easier to ignore. Take the San Bushmen of the Kalahari, for example. Botswana to this day sticks them into "resettlements", appropriating their ancestral land and forcing them to give up their culture and language to "bring them into the 21st century". Once resettled though, they're left to slowly starve, die of disease or drink themselves to death. Most Botswanans sleep easy though 'cause after-all, "they're only helping them move with the times" ... whether they want to or not. And the rest of the world remains ignorant of it.
Apartheid brutalises people by not only attacking them physically but also undermining everything that makes them who they are, stripping them of their language, their cultural background, everything. When you reduce people to pure survival by "resettling" them in desolate bantustans or routinely bombing the crap outta them or sticking them in camps, you dehumanise them and nurture the very worst in them. When you keep treating them like caged animals, eventually that's all you get, wild and violent. My generation grew up knowing nothing but violence. White kids were sent off to the border to fight the "black menace" in the most brutal ways imaginable while black kids grew up with little besides police beatings and "pass laws" and slow starvation to look forward to. They were provided next to no education, restricted in movement and crammed into dense slums that were passed off as "independant states" to the outside world. Basically the apartheid government took the worst of what growing up in a gang had to offer and applied it to an entire nation. Those kids grew up to be amongst the most violent men in the world? Men in this country are 9 times more likely to commit rape and murder and assault than the rest of the world because it's all they grew up with.
Genocide is a visible evil, one we all recognise and hopefully have a visceral reaction to, but often apartheid isn't. It's often hidden and quiet and just "explained away", and some of the most terrible things it does to people only come bubbling up much later. They're related, sure, both born of xenophobia, and apartheid all too often eventually becomes genocide, but unless one recognises the differences between them, it's all too easy to miss them or misunderstand the situations that give rise to them.
Mina.
PS. ZA and the US aren't uniquely guilty of apartheid either. Australia did it to the Aboriginal people there, as did the British in India, and Palestine, and most of Africa ... just about everywhere they planted a flag. Not to mention the genocides the Belgians perpetrated in the Congo, or the Spanish and Portuguese in South America ... we have a LOT of collective blood on our hands.