I've read a number of books and novels by Harry Turtledove. He is the one of the best science-fiction authors who has carved out a niche in writing alternate history stories. Earlier this week I finished reading his epic 11 volume set about America.
His premise in the first book (How Few Remain) begins with looking at what might have happened if the Confederacy managed to keep its independence. The rest of the novels follow an 80 year history of the North and the South co-existing in North America. He draws in Canada, Mexico, and the Mormons as recurring people and places of interest. In the earlier volumes Germany is mentioned, and takes a back seat until the final two volumes when important developments in Germany reverberate in North America.
His saga is divided into four groups of volumes.
Volume 1: 1880 (How Few Remain)
Volumes 2-4: The Great War
Volumes 5-7: American Empire
Volumes 8-11: Settling Accounts (World War II)
If you'd like to ponder what things might have been like if the Confederacy remained independent, Abe Lincoln was never assassinated, George Custer didn't die at the Battle of the Little Big Horn, an independent Mormon State in Utah, an alliance with Germany in World War I, and many other twists and turns that span the years from 1860-1946, then check out this saga.