The early 60's nuclear threat film fail safe (sadly buried in obscurity by the much more popular Dr Strangelove), has the US mistakenly launch a nuclear bomber squadron into Russia. In efforts to avert disaster the US and USSR co-operate on shooting down the bombers but one survives and approaches Moscow. In a very chilling final sequence Henry Fonda as the US president is linked up with the Russian leader and the American Ambassador in Moscow and the Russian ambassador to the UN in New York. When the American ambassador's phone becomes a screech indicating the successful detonation of the nuclear weapon over Moscow Fonda orders a bomber piloted by a friend of his to drop a nuclear weapon over New York.
My question is, if this desperate scenario was worked through, what would have happened next?