The challenge, should you accept it, is to have the US decend into a second civil war by the 1990s. You can chose the POD anywhere after 1945.
Wow, scary.1961: A high-brass Soviet General develops a syphillitic madness. He hijacks the Soviet nuclear facilities.
The USSR begins a nuclear war with the USA against the Kremlin's will.
The entire industrialised world is destroyed.
1990s: The remnants of American society have pulled together and began to fight each other over who has the right to reform the United States.
Simplist way would be for a rogue government attack, a terrorist strike, or the like.Well Dean, I didn't specify the mode of the civil war... and also, I like the ideas you propose. I wonder though, what do you have in mind for a decapitation strike?