An alternate timeline at another board i've started to hang out at that goes about a different tack: what if the Halifax-Butler coup succeeded, resulting in a Britain that made peace with Germany?
The Big One .
ignore the prequels (everything before the titular 'The Big One', they're mostly background on that timeline's somewhat unusual characters, but they're largely unimportant in the base story and feature more prominently in the sequels).
Spoilers:
Essentially what happens is that, with the British out of the war the US begins to focus chiefly on the Pacific, basically heading off any possible Pearl Harbor. Germany attacks the USSR as per OTL except they capture Moscow; Stalin dies, Zhukov takes charge. In 1942 Germany asks Britain and Vichy France for troops, they refuse, and Germany invades them. The Royal Navy stages a 'breakout', taking the Royal Family along with quite a few important people and equipment. Many of them end up in the US. Germany demands the US hand them over. FDR says 'Molon Labe', the Germans decide to take him up on it and thus the US is dragged into a very bloody war, with US troops serving with the Russians on the Eastern front, and a very nasty sea war. Come 1947, the US has produced a large number of atom bombs. 200 of them are dropped on Germany via B-36s, ending World War II even if a few German troops (in warlord-states carved from the Ostfront) still fight on until 1960. Even then, some Germans end up as janisarries to the new Caliphate, which together with a Japan that absorbed China constitutes the bulk of a big mean US's worries, along with those of a de-USSR-ified Russia and an Indian/Thai/Australian alliance (an odd construct cobbled together by the aussies, british expatriates in India, and one very devious thai negotiator (Gandhi dies in an 'unfortunate' car accident).
From that point forward, it's basically an exploration into a world in which the authors' views are extended, or a more conservative kick-ass America and allies, an irrelevant, very peaceful Europe (Germany is peaceful indeed), and a real bias in favor of strategic bombing (Curtis LeMay becomes a celebrated US President, and in later times a sort-of saint). The odd bits are due to a series of immortal characters (so-called 'demons') who are in some cases thousands of years old and tend to work as private contractors (who by the 1980s basically run the government, which largely did away with civil service). Everything is effected, from the massive 1960s-type high-speed/low-quality cars to the hard-drive-less network computers to the orbital bombers.
