Not an easy challenge.
-Confederate independence permits Kentucky, Missouri, the original 11 states, Indian Territory, and both Arizona and New Mexico to join the South. Strong sympathetic populations remain in Illinois, Indiana, and Maryland.
-Confederate economy develops unusually well and offers Maximillian of Mexico cash/credit (based on tobacco and cotton) in exchange for Sonora, Chihuahua, and Baja California along with responsibility for Benito Juarez.
-Dominican Republic joins Confederacy in exchange for debt relief in 1868
-Spain and the US argue over compensation for the Amistad for decades, when diplomatic trouble stirs the Spanish sell a rebellious Cuba to the Confederacy largely to spite the Union, however they keep Puerto Rico.
-Confederate troops invade Haiti after "incidents" along the border
-Central America is gradually turned Confederate as first Nicaragua then other nations ask for help in their civil wars only to find themselves made states as a result
-Confederate abolition comes on January 1, 1890 following negotiations with UK, France, Brazil, and other global powers
-With the UK in the north and Confederacy in the South, the Union falls under a Socialist regime in the 1890s and begins a generous welfare system. With the depression of 1907 it causes near-bankruptcy and destabilizes the dollar while the Confederate economy is much more stable and climate much more amenable. Migration results, especially into Florida and Cuba but noticeably into most states.
-World War I sees the Confederacy involved as an indirect participant early in the conflict, becoming a breadbasket and financial haven for Allied investments. Coordination with London and France permits breakthroughs in chemistry, permitting a slowdown in the spread of the boll weevil and permitting a difficult but effective transition to other crops while eradication efforts of the "damned black beetle" begins.
-Confederate construction of the San Carlos Canal in Nicaragua brings in enough revenue to save the government from bankruptcy following the weevil concerns
-Mexican Revolution causes Yucatan to break away after the Imperial family is forced to flee, Victoriano Huerta seizes power and the Yucatan joins the Confederacy in exchange for not having to rejoin Mexico
-Confederate immigration of European refugees fleeing post-war conditions provides an influx of engineering and mechanical skills. Education gains importance as they bring different social values with them and begin agitating for more opportunities for the non-elite
-Roaring 20s are good for all, while the US experiments with Prohibition the Confederacy is happy to provide liquor while maintaining tight internal controls. Bourbon and whiskey become lucrative export products.
-Confederate ambitions in Mexico gain traction as Imperial family of Mexico regains the country following a revolution in 1926. Huerta raids Hermosillio and Chihuahua and causes Confederate intervention, leaving the Empire of Mexico all but a satellite of the Confederacy.
-Second American Civil War in 1929 stalls further US economic depression as an attempt to revitalize their economy, the results are bloody but with the Treaty of Cairo in 1932 realizes the state of Cahokia (southern third of Illinois combined with southern quarter of Indiana), Kansas, Maryland, Delaware, and the southern quarter of Nevada as Confederate possessions with the establishment of an independent Deseret out of former Utah and western Colorado. California and Nevada are permitted a plebiscite on independence which is defeated by a 62% vote, more in favor of independence than initially predicted. US capital moved to Omaha for defensive reasons.
-World War II follows a less rocky Great Depression and sees the US still trying to recover and staying out of the conflict, California (+Nevada) secedes of its own accord this time and joins the war effort with the Allies. Confederate science and engineering make great leaps forward, especially after a second larger wave of refugees comes across during and after the conflict. Over half of the population is now immigrated or directly descended from one of the two waves of European immigration.
-By early 1962 the Confederacy is taking control of former Caribbean colonies and California is growing close enough to the Confederacy that talk of statehood abounds. Mexico is all but a Confederate territory though officially the Imperial family, now infused with Confederate blood, retains control. Deseret and California bring in large amounts of mineral wealth though the election of Curtis LeMay to the presidency of the United States leaves many fearing that war is on the horizon. However, the formation of the New England League, Great Lakes Association, Rocky Mountain Militia, and Cascadian Brotherhood mark the possible dissolution of the Union if another conflict comes and fails.