Ever read Harry Turtledove? He actually explores that stuff in his “alternate history” novels.
In one, because the south won the civil war, the entire continent split and the result was that during WWI the north supported Germany and the south supported France/England. There was an American front.
By far, his best book is Guns of the South. A bunch of South Africans from 2015 go back in time and start off by, right after Gettysburg, give Lee 100,000 AK 47’s. The impact on individual battles as well as the “secret” response of Lee is a fascinating read. There is one great line where the “riverton men” (the guys from the future) have these simply amazing rations that Lee and others are mesmerized by. They’re called “Cup-o-noodles”. :)
His later books are in multiple volumes and cover post-civil war, WWI and even WWII. In WWII we are invaded by aliens in 1942 (IIRC) and suddenly everybody is working together - sort of. It was interesting but after a while I felt like I was being strung along, as is done in so many modern TV shows.
“... give Lee 100,000 AK 47’s.”
Did they remember to bring the mags and the ammo? /s
Yikes, a hundred or so modern automatic weapons would of changed to course of the war.