This is a topic on which I would like to invite input from other users. I have an outline of a number of basic events I want to happen, but I need advice on how to put it all together. I'll outline here the background, and solicit discussion on the discussion page.
As in OTL, the United States was divided into two broad regions that differed primarily in the legality of slavery and the concomitant economic differences between them. Unlike OTL, the United States did not retain possession of the Great Lakes region, which had become the independent, Swedish-speaking Confederation of Svensland, which prevented the formation of free states in the area, and hampered the westward movement of American pioneers (one notable exception being the Mormons), and thus, prevented the formation of many states in the west. This caused a few problems with the political compromises on the issue of slavery, because a balance between free and slave states was more difficult to maintain. Delaware and Maryland were eventually required to outlaw slavery to balance the addition of slave states such as Louisiana and Arkansas.
The balance in the government also leads to a disagreement over what to do with Texas. Northern states prevent the annexation of Texas as a new state in 1845. Thus, it remained the Republic of Texas, and its political relationship with the United States was left somewhat unclear. The character of the Mexican-American War was consequently also altered, such that Mexico retained the California Territory for some time.
The Mormon Church was still founded in 1830, and, after failed attempts to settle in Yngstad and Missouri, moved west, settling in the Salt Lake Valley in 1848. Once there, they found themselves a focal point in the Mexican-American War (during which they attempted to remain neutral, then declared the independent Republic of Deseret, with the never-fulfilled intention of joining the United States as the State of Deseret). The Republic of Deseret, including Nevada and Utah, along with parts of Wyoming, Idaho, Colorado and Arizona, would remain an independent republic.
In the wake of the Gallic and Iberian Civil Wars of 1752-1770, the bulk of Spain was united under the Kingdom of Andalusia, which retained all of Spain’s overseas territories that had not been taken by the French, British or Portuguese. The Andalusian state showed greater interest in its American colonies, and made more extensive use of Florida and Cuba, establishing amicable trade relations with the Seminoles of Florida. The tendency of the Seminoles to accept escaped slaves from the South led to conflicts with the United States, but the practice was effectively stopped by a joint American-Andalusian agreement in 1795. However, freed slaves would again be accepted by Florideans in the 1850’s and 1860’s, and would contribute to the American Civil War.
With the western territories and autonomous republics remaining in their liminal state in relation to the Union, and with the uninhibited expansion of the South and Southern ideals toward the west, the American Civil War would take on an entirely different character. The combination of the Union, Svensland and Florida would not be sufficient to put down the rebellious Confederate States of America during the Civil War.
Svensland joined the Union cause only after the Union agreed to sell the Iowa Territory (consisted of all the land between the Mississippi and Missouri Rivers, excluding the northern half of the State of Missouri). The contribution of Svensland to the American Civil War was a campaign in Arkansas, Missouri and Louisiana that resulted in the disintegration of the states of Missouri and Louisiana, and prevention of the merger of Confederacy and Texas.
Missouri north of the Missouri River went to Svensland as Nordmissouri; Missouri south of the Missouri River and Arkansas north of the Arkansas River were combined with Oklahoma, Kansas and Nebraska into the Confederation of the Great Plains, an Indian country; Arkansas south of the Arkansas River and Lousiana north of the Red River were reorganized as the Confederate State of Arkansas. The Republic of Texas gained control of the remainder of Lousiana, minus the small section east of the Mississippi River, which fell into Floridean control, along with the rest of the Confederate Gulf Coast.
Kentucky becomes a Confederate state, and West Virginia splits from Virginia to join the Union. The Confederacy continues to exist as an independent nation today.