Ok, This sounds like fun.
So using the dates on the map and making this up as I go.
so Things go along just fine until Vermont settlers decide not to join the USA some one decides that the constitution presented in 1787 would be bad for them and they just play it low. the USA doesn't really care, the UK doesn't really care, right now...
Things hum along until Mr Maddison's war and the Heartford convetion (happening in 1812 for some reason...) is successful and Federalists take new england with them. Oh snap! The Brits Force a harsher peace on the usa and recover Louisianan. But because of the heroics Of Old Hickory and his Creek and Cherokee allies the Brits cant take all of Louisianan back, just that little pink part. the war of 1812 ends in 1813, DC and York are not burnt down (Canadians lose their military claim to fame to hold over the Yanks.)
then Congress of Vienna happens the UK gives Louisiana back to France, which loses Louisianan to an internal uprising. Yankees, Brits, etc use it as a key location. Lousiana allies with the USA but remains independent.
Then the mexicans rise up! By 1821 they have earned their freedom, Santa Anna and all that stuff.
Jackson is elected in 1824, Trail of tears is 1832, one of Jackson's last acts, the 2BUS still lives! The Democrat party doesn't form. the Republican party (Jefferson's) survives... for now.
things trudge along, slavery is a growing issue, but a free Louisiana kinda caps things. Southerns pour into Texas because mexico is worried about Louisiana's ties with the UK might make it a base for moving in on the east, while Oregon is a base for moving in north. Yankees tend to migrate to California. Also, Mormons happen, but no one likes them because they marry all the good women (this is tongue in cheek, i just realized that as part of my massive deficiency in antebellum studies is i know next to nothing about the Mormon genesis....)
Well the new texans dont become catholic, nor to the Yankees in California, Bidwell-Bartleson, Sutter, and others are playing nicely, if left alone.
The texans go first, Mexico outlaws slavery, bang bang, pow, pow, The alamo is lost, but they capture Santa Anna and force a peace. This destabilizes things in California allowing an uprising there of Californios and Yankees.
While this is happening, the Mormons are moving to Deseret, and the Qubequios and Canadains are demanding more autonomy. It comes to blows and the UK sets up two dominions down linguistic lines. President Polk who survived William Henry Harrison death in 1840 (still one party, but the party is splitting between Van Buren and Clay factions) makes a treaty with Britian over Oregon, neither of them can secure Oregon so they set up an autonomous Joint Dominion.
The maritime provinces are spun off too because London is unhappy with what Canada did and decides to keep it small as possible and play the pieces off against each other.
Further Indian removal by the Americans in the south east shove many into southern Florida. It becomes an autonomous reservation until the end of forever.
1850s, California and Deserete break away from mexico, the places are too far from Mexico City to really care about for Mexicans. California is far less racist because of the lack of Yankee and Southern immigration. Gold isn't found until the 1870s and by that time they have begun industrialization. Sutter and Marshal pick a different location for the saw mill where Marshal found the gold.
Well, the Republican party has fractured in 1856 between the Aboltionist/Business factions and the Agrarian/Local Control factions. The Clayites and the Jacksonians. the election of 1856 with Lincoln vs Davis is very close, but Davis wins and tensions fare, Stephan Douglas, a member of the Jacksonian "Democracy" is eyeing 1860 and he needs to make a name for himself. He doesn't care about slavery, he does care about checking the power that the Federal Government has been acrewing under the Clayite National Republican faction. He pushes the Kansas-Nebraska act to expand slavery but makes a deal with Charles Sumner to fund a train across the Mississippi at St Louis. Sumner wanted it much further north, but his hopes that he could stop the spread of slavery caused him to compromise.
Kansas erupted in pro and anti slavery violence, John brown (he wanted to move west, so he immigrated to the USA in the 1820s), his raid on harpers fairry. (There is no william Lloyd garrison here, he oppses slavery, but that's in the USA, not New England... He writes against it in his paper, "the Boston Sentinel" but doesn't go and bother to tell America it's business, just tries to set a good example)
1860 the National Republicans and the Democrats (see what I did there

) face off again and John C Frémont wins! he was a dark horse canidate in the nomination.
The south despises a full blown publicly vocal abolitionist and they start seceding. Fort Sumter, and war. Frémont is much more aggressive than Lincoln. He sends in forces and the Union starts getting its clock cleaned. He makes the war about Slavery up front just as much as it is about keeping the union together. in 1861 he authorizes negro regiments and thousands of black men join up to fight. White soldiers begin deserting. union forces are in disarray and Confederate forces lay siege to DC in 1862. Robert E Lee captures the vice president on his way out, Frémont goes far to Lead forces in Pennsylvania, which turned out to be a Feint.
The Treaty of Richmond 1863 Formalizes the independence of the CSA. President Lee is elected in 1866. Frémont runs as a National Republican in 1864 after forcing through the 13th amendment which abolishes slavery and formalizes his 1861 emancipation proclamation (only with 9 fewer states in the union). The 14th amendment was ratified in 1865 which formalized equal rights for all men. (womens rights activists said this was a travesty! Fredrick Douglas in Hartford wondered what took the USA so long, New England did this in 1831)
in 1864 Frémont was humiliated as being "The man who lost the south" and he was steamrolled by John C McClellan who "would have whipped those Rebs!" He went on to a lackluster presidency, two terms with no scandals, very little to point at other than to pay down the war debt. That money went on to fund Industrial growth in the north. Railroads grew out through eastern Iowa by now. Mechanized farming started picking up.
The Treaty allows the CSA thave sway over south Florida. West Virginia joins the USA. the USA gains access rights through the msisissippi so they can trade in New Orleans. the CSA gets Ohio river access for trade with New York and New England (who really likes southern Cotton still).
The Dakota Treaty of 1876 under president McClellan recognized the rights of the locals to autonomy. with no transcontinental railroad there were very few whites out there and no one knew about the gold except for old John Stonesmith who said the black hills had gold, they assumed he was touched.
Canada does something similar with the Metis. With out "Sea to shining sea" for either the USA or Canada there isnt much western movement, at least, not in the 19th century...
in the 1870s and 1880s econmic growth guided by the 2nd Bank of the USA which republicans have continually rechartered, although Van Buren and Jackson both tried to break it, the USA used its larger resources and land area to catch up and surpass New England. Immigration from europe is mostly split between New England and the USA, USA has more farm land, the NE had more factories which colored their cultural outlooks. the USA was urbanizing at a faster pace by the 1890s but they were a good bit farther behind.
Southern Industry is booming as well. They need local machine tools and Guded under Presidents Lee and Forest economic growth, aided by British and New England investors allows their plantations to start to mechanize. They are far more decentralized than the USA and as a result their industrial power lags behind, but they become a major textile producer. Poor women and Free Blacks are the major textile laborers by the 1890s. Because of growing urbanization and the embrace of Racial Nationalism more and more Blacks leave the south to move to the USA but this causes the United State's First Immigration laws. the Negro exclusion act of 1894 limits the number of "confederate citizens of the Negro race to 1% of the 1870 census of negro population of the United States per year." The Office of Immigration is established to keep black men and women out of the north (it also helps to keep wages from being suppressed.) As a result books by Marx and Alan Parsons become very popular in the Factories in Atlanta, Birmingham, Charleston, and Richmond.
California gold rush doubles its population in 1 year and again in 3 years. the vast influx of money allows it to crash industrialize, not as a state initiative just floods investors with cash. Theodore Judas's Valley railroad company explodes along with a dozen other new lines. California goes from a small ranch economy into a thriving trade and Fruit economy, refrigerated steamers allow the pacific market to enjoy its fruits, vegetables, and nuts.
The Treaty of the West initiated by California but Agreed upon by Deseret and the USA created a tri-partisan right of way to build a Rail road from Iowa through Salt Lake City and through the sierra Nevada using Jim Beckworth's trail and terminating in San Francisco. Three rail companies are established, the California Line, run by the heirs of Theodore Juda, the Brigham Young Rail company through Deseret, and the Union Pacific through the USA. this was finished in 1881. Nitroglycerin and less corruption allowed it to be built much faster and with alot more private money. With out the state sponsorship the railroads don't gain a monopoly, at least in California. the octopus is prevented.
By 1890 the CSA realizes it needs a pacific outlet so They emulate the pact that California stated. Using its influence with Louisiana and Texas, the three of them bribe the Mexican govenrnment to allow a right of way to the west coast of Mexico. Like Guantanamo Bay in OTL, the CSA had the right to a city on the coast of the Gulf of California. They use lots of Black labor to build the rail road through the 4 political units and by 1897 they are running Trains from Richmond to city of Davis, named for the late President and father of the CSA (by this time Davis's fair treatment of his slaves has become a powerful propaganda tool. Slavery is ending, more and more plantation owners are selling their slaves for "mechanical Negros" as the tractor factories call the cotton pickers. Slaves are bad for factory work so the slaves are emancipated and turned into contracted hired labor, that is they must work but their contractor doesn't have to feed, clothe, or support them. This industrial sharecropping remains until 1914 when the CSA gets involved in the first world war as they are very tight with the UK and France. the CSA rounds up all the marxist and other communist Blacks, drafts them and ships them off to France where most go awol and cause problems for the French defense. They end up in switzerland and try to work with other socialist anti war protesters. Because of slave labor the south had very limited immigration from Europe. They have a major labor shortage which pushes mechanization.
Because of the "negro problem" world war 1 ends much quicker than it should have. German breaks through the lines that the CSA black troops disrupted and forced a more amicable peace. The problem is it ended in winter of 1914. The bloodlust was still boiling.
By 1920 another trigger starts another major world war and things were learned from 1914 about fast action and troop movement. Airplanes are better and so are trucks and these new armored cars with caterpillar treads on them...