Your challenge, if you choose to accept it, is to have a majority white (plurality if you include East Asians) and English speaking country, and a former British colony, go the way of much of the Third World.
With a POD after 1865, to avoid the standard Confederate option. While a balkanized South Africa could work, keep in mind that it must be English speaking, and there is no way OTL's South Africa could meet the standards of the challenge (White majority- ha.)