There is a novel from the 1970s in Britain during the Enoch Powell immigration scare period by Christopher Priest of "The Prestige" fame about a nuclear war between South Africa and its neighbors leading to a mass flight of refugees from Africa to other nations around the world. In the book, a right wing xenophobic government under a Prime Minister named John Tregarth who bares a suspicious resemblance to Enoch Powell leading a Nationalist Party which bares a suspicious resemblance to the National Front came into majority in Parliament shortly before the war and the refugees arriving. The African refugees are treated much worse than other nations they arrive in and militant groups are formed with aid by survivors of African militaries. The militant African refugees receive arms from the USSR and begin forcibly occupying houses in London and other areas and liberal or civil rights sympathetic elements of the constabulary and Royal Armed Forces secede and join them and a civil war begins in the United Kingdom.
The protagonist is a philandering college professor whose house is taken over by armed African refugees and is forced to become a refugee himself, being harassed by the Nationalist government, the African refugee army, aided by the British secessionists and obstructed by the UN and others. He joins an organized group of refugees after leaving a UN camp, then his wife and daughter are abducted by the African guerillas and he sets off to find them, leading to a pretty scary ending.
The book is interesting in AH terms for showing in graphic detail a bloody Third World style civil war in a modern first world country, complete with USSR sponsored left wing guerillas and a right wing authoritarian US backed regime, UN refugees camps and Blue Helmets and starving desperate refugees and how they survive.
Can anyone think of similar scenarios that would lead to modern civil war, anarchy, failed state status, UN intervention in the US, France, UK, Canada, Australia, etc.?