The actual loss of the Civil War by the North(ern aggressors) is detailed in Turtledove's book, "The Guns of the South." FYI, it occurs because some pro-Apartheid South Africans in an alternate future take a trainload of AK-47s and ammo for them to General Lee. A very interesting (if implausible) read, which I found better for its analysis of a Southern victory's effects than for the technological/sci-fi aspects.
For those Yankees that may disagree about who started the War, please note that I used to be one of you. A fair analysis of the facts leading up to the War of Northern Agression, which was instrumental in the destruction of the federalism set up with great care and deliberation in the now-dead U.S. Constitution, shows that events were very much different than the history books represent. Oh, and BTW, if you Yankees ever try to repeat that event, the thing will turn out quite differently. The South is far more populous, industrialized and armed than 144 years ago.
From the Library Journal: "In 1862, the Confederacy won the War of the Rebellion (not by interference of time travelers, as in Turtledove's Guns of the South, LJ 9/1/92, but by their own skillful military and diplomatic efforts). The defeated North has stewed for nearly 20 years. In this alternate history, the South exercises an opportunity to purchase Sonora and Chihuahua from the bankrupt Mexican Empire, having already wrested Cuba from Spain. James G. Blaine, now president of the United States, arrogantly seizes upon this pretext and invades with the aim of reunification. Lincoln has become an outcast of the Republican Party and preaches socialism while Custer is a frustrated and embittered colonel on the frontier, Samuel Clemens a fiery newspaper editor in San Francisco, and Rosecrans the inadequate head of the Union Army. Turtledove is an accomplished professional at this sort of thing and has given us an entertainment that makes us think somewhat about why we are the way we are."
From Booklist: "The year is 1881. Lincoln, since losing the Civil War and then the presidency, is an itinerant socialist speech-maker. In the Confederate States of America, President James Longstreet buys northern Mexico, and the U.S. president declares war, the course of which operates through several historical figures. In San Francisco, antiwar newspaper publisher Samuel Clemens talks himself out of seditious trouble with William Sherman, while the British fleet reduces the city to rubble. The British/Canadian invasion of Montana is stopped by Teddy Roosevelt, yelling "bully" constantly, and by George Custer, whose brother Tom dies, reappears, and then is later referred to as dead. The War in Mexico goes worse for the bluecoats, as would be expected, since they face the dashing, slashing J.E.B. Stuart and his "camelry" --whether their mounts are dromedaries or Bactrians is unclear. At Louisville, Stonewall Jackson reprises his successes by repelling the Union attack and capturing Frederick Douglass, war correspondent."
It's worth the read for anyone interested in history.