Just picked up from the library "Without America", a SF novel by John Birmingham. He's written 'Weapons of Choice' which I read about half of before I couldn't take it any further so I'm not sure how this is going to go.
WoC had the fault of being overlong in many sequences, and its 2020 US Navy went back to 1943 ish, and they were fair to everyone but the Americans of 1943. Its interesting, they wanted to understand everyone, but their own ancestors. That type of multiculti nonsense ('everyone's equal, except America which is worse') is tiresome.
WA has the premise that some wave of energy zaps America and the rest of the world goes to pieces.
1. Like in SM Stirling's 'Dies the Fire' we have a replacement for the Mad Max post-apoc SF stories. Instead of a nuclear war or bioweapon doing in everything, we have Bizarre Forces Out of Nowhere as the new trope.
Harry Turtledove wrote a series of what happened when alien invaders with 1960 ish tech invaded in the midst of WW2. One of the best scenes was when a Big Bertha type over the horizon cannon dropped a shell right on top of an alien spaceship that had landed.
This opens the door for some ReMixes.
Alien invaders
WW2
Bizarre Forces Altering Rules of Reality
BF destroying major component of scenario
And there are a lot of other weird mixes than the ones I've mentioned.
But using the ones described:
What if Nazi Germany in 1943 got hit by an asteroid large enough to devastate it to the point where government beyond the village level ceased to exist? Obviously, France and Poland are also pretty hard hit.
I'm not sure where the major allied forces are at this point in time. Whoever has ready to move forces could radically alter the world as there is a vacuum of power.
One effect is likely another Year Without A Summer.
Would Shintoist Japan decide this was a sign from the gods, and sue for peace with conditions? Would America accept such an offer?
Do the imperialist Communists grab as much territory as they can, and the Americans largely acquiesce? Does this kick off a Second Russian Revolution (abetted by the extremely poor crops from Communist growing techniques and the Year W/O Summer and the end of American food subsidies)?
Does the attack on the Communists bring the 1960's Anti-war Movement out in full flower in 1944? And given that people like FDR (who interned the Japanese) are a lot more hardnosed than the leaders in the Sixties were, what happens then? I could see a nascent peace movement being dealt with by prison terms and 'sabers drawn'.
It'd make Kent State look like small potatoes.
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Or what if the V (remake is coming out on TV soon.) came during the Summer of Love?
Or what if a major asteroid smacked the Pacific shortly after the declaration of war between Japan and America. Hawaii is gone, Japan is mostly toast, the American West Coast is gone up to the Sierra Nevadas, and major pars of Southern China and Vietnam et al are smashed. Ring of Fire volcanoes kick off (another Year W/O).
At that point, Russia and Germany might ally with Russia taking China and Germany going for the Brit Invasion and 'generously offering to the devastated and mislead peoples of the US a chance for negotiated peace'.