PoD - Manhattan nightmare.
US atomic weapons research goes seriously awry in '42 at the early stages, a critical mass detonates in (pick a large city - I go with chicago, but you can pick your own, NYC is a poetic choice, given the 'manhattan' project) Chicago.
The city is reduced to a radioactive wasteland, destroying large chunks of American industry and breaking the national will to survive. America accepts terms equal to the wildest dreams of Tojo's imperialists, and withdraws to Hawaii. Alliance with UK (blamed for goading the US into the war) is shattered, US turns it's back on WW2, and on the world in general, becoming grimly isolationist, and focused narrowly on the western hemisphere.
As the war in Europe drags on, the US acts to prevent further involvement by expelling European colonies from the caribbean.
The inevitable long term result is another war with british north america. Early successes lead to an exhausting and debilitating long term insurgency and campaign of suppression and relocation.
By 1960, the US is a second rate (at best) power in a world increasingly dominated by India. Society is isolationist, racist, casually brutal, and strictly monitored. Separatist efforts in the northern territories (former canada), Cuba and the south west simmer, race riots (this US never had a civil rights movement) drain more blood and periodically destroy the proto-formations of black and hispanic middle classes. Separationism is "finally" put down in the mid 60's by mass deportations - canada in particular is largely emptied out, as canadians are forcibly moved to the the south and southwest.
By the late 1970's even this grim balance begins to shatter. The is no more money to fund the armies, and too few young men willing to kill on behalf of freedoms they've never enjoyed. The first rebellions start in Alaska, Hawaii, and Cuba - farthest from the center's of power. But once the dam breaks, the desire for a return to misremembered times before the wars runs wild.
By 1985 Alaska, Hawaii, Cascadia, California, Texas, Cuba, the New Confederacy, New England, and Quebec are all independent.
By 2008 the rump US is regarded much as Russia today - a corrupt and ruthless state in the process of decline, granted importance only due to strategic position, brutal tactics, and near monopoly of critical resources (breadbasket for much of the world).
The end to US aid / convoys screwed the UK logistics beyond repair. In 43, after the final collapse of the African front, Britain comes to terms - the empire is over, what remains of the RN is scuttled, Ireland and scotland recieve illusory independence (they, like the rump English Republic, are permanently under the thumb of the Greater German Reich and their fellow puppet states in the European Protectorates. Stalin never received the supplies needed for the Red Army's push. The Soviet/Nazi front deadlocked in mid Ukraine, with Europe and Russia both gradually impoverished and emptied to feed the steppe meat grinder of their leaders' ambitions. The long war, which will define western Eurasia for the rest of the century, has begun. Coups & countercoups ripple through both sides, and over time the transformation of both into Nationalist-Militarist-Socialist-Totalitarianism differentiated only by the language of their rulers is widely recognized by those lucky enough not to live under either regime.
Mao & CKS continue their drawn out insurgencies against the Japanese, with both sides descending in a spiral of increasingly bloody and barbarous reprisals. Eventually the Japanese resort to nerve gasing rebellious villages. The war winds up in the late 50's due to mutual exhaustion - Japan has no more sons to die for the emperor, and coastal china is a wasteland of lingering toxins and burnt out cities. Japan faces a grim future, as the rising Chinese states, and the emerging Indian "Greatest" power view it with unbridled loathing.
An impoverished military dictatorship holds on in Japan and Korea until the Indo-Arab wars of the late 70's and the resultant oil shocks shatter the regime, just one of many casualties - a fragile regime held together by suspicion, fear, and propaganda.
... ok, so I'm feeling gloomy today. I'll go for cheerful tomorrow.
