This is just what I think would be going on/ going to happen a bit after Monsieur‘s collapsed South Africa video.
In terms of their Relationships, the west cape republic and the boer republic would be allies on the premise that the majority African population hated the minorities inside so other than Transkei (which would be generally passive to 4 of the nations excluding the boers) so does two would generally get along since the cape gets a buffer state and trading partner and the boers don’t get surrounded and a ally in this aggressive region.
other than Transkei, all the African majority nations around would controlled by dictators and generally just be poor, while carrying resentment of the boers with them.
The west cape would still keep the foreign relations I stated above but through trade from the Boers, the business that would probably spring up from its population, and the boers wanting it to stay stable would probably get a efficient government that mirrors Rhodesia.
Transkei (other than maybe the west cape) would probably be given the most international sympathy mainly because of Mugabe, and even though it would have the resources South Africa had I think it would’ve remained stable and have consistent growth while Mugabe was alive. When he dies either he would been able to pick someone reliable enough to replace him by building support for him years before or the nation would have a dictator like the other African states.
For the first few years The Boer Republic would be given sanctions which would’ve strangled the economy but because of the skilled labor that would be emigrating to it from around Africa it would stay stable. After which looking at the map the Boers after settling disputes would be the best well-off out of all the nations. Politically it would be a bit fascistic in the start but as elections start the party’s that would be in control would be like Poland’s or Hungary’s current main party’s. It would be given massive amounts of white farmers from around Africa would would mean the nations around it would soon rely on it for food. But the main resource that’s gonna make them so dominant is the fact that most of south Africa’s mines (the most important in this case being platinum) are located and controlled by the Boers. Where they would have control over the vast majority of the worlds platinum supply, where they would sell it through there white list and even back their currency with it since they control the majority of the supply and production of this one rare resource. Although there would be a lot of paranoia on there border with the African states. wondering when or if they’ll ever attack. for some inside the country they’ll also have that same view with the cape but it would be smaller.
Not sure about the US. It would still flame ethnic tension there and maybe get bill Clinton to scale back on immigration if it gets bad enough. Although I think the after Bill, Bush would lose the primary and be replaced by Buchanan (Or at least I hope. Thats being based on the increase of ethnic tension and that older style of the right returning)