As has been said, using too many OTL internal borders is going to get you in trouble around here, and smacks of quick-n-dirty rather than thought out borders. For instance, the boreder between USA and Canada down the St. Lawrence river, which ignores the fact that much of its southern bank was settled by the French long before your POD and has no cultural, linguisitc, or political connection with Boston or New York. New Brunswick didn't even exist until after the ARW when Loyalists from the 13 Colonies relocated to Nova Scotia (which included NB at the time) made for a population large enough for its own polity.Being Australian I didn't spend a tremendous amount of time studying American history. However from what I can figure the North American Continent could easily appear like this.
How likely would the following outcome be.
USA wins ARW. New Brunswick and Nova Scotia join the union. Also Maine, NH, Vermont and NY and New Brunwick manage to push their borders north to the south shore of the St. Lawrence River
Due to rising cost and shrinking profits Britian passes the The Slavery Abolition Act in 1806 helping the ACW to be bought forward to 1809.
After heavy fighting that lasts only two years The CSA and USA grind to a stalemate and call a ceace fire thus partitioning the the nation into two Soverign nations
Sensing weakness in the USA, It is Britain that starts the war of 1812. After heavy fighting the British cant retake any land in the St. Lawrence River area and instead sweep south, west of the great lakes area and take what would be the OTL US states of Nebrasca, North and south Dakota, Minnesota.
Fearing A loss of even more territory the US sues for peace and is forced to cede Iowa.
After the war of 1812 USA and CSA fearing a more agressive Britain sign a memorandum of understanding that puts aside past differences and the two nations enter a common defence agreement and establish a commonwealth. Over the next few years, slavery is abolished in the CSA and the two nations begin acting as one nation in all but name.
After a bitter struggle the Treaty of Córdoba is signed in 1821, ending the Mexican war of Independance.
In 1826, anglo leaders in texas begin inviting settlers from British North america (BNA), USA/CSA and Britain/Ireland. Mexican Officials are unhappy with this move and start imposing economic and military sanctions on the area.
1828 a small community near San Marcos Texas, Riots against Mexican authorities and is butaly put down by Mexican troops. Similar riots over the next few years are dealt with in the same fashion.
Gold is discovered in california in 1823, aprox 25 years earlier than OTL. This brings a massive influx of ppl from BNA and USA/CSA as it did in OTL. Within two years the population of Califronia swings fom 75% Hispanic/amerindian to 60% Anglo. Again Mexican officials impose sanctions and taxes on the local populations as they did in texas.
After 15 years of opressive mexican treatment the Texans are ready to cede. They have been secretly plannining with Caliofornian and British ambassiders on a plan of action. In september of 1835 Both Texans and Californians jointly announce their ceceation from mexico. Californian gold is used to pay off some mexican military leaders and due to internal struggles the mexican government is powerless to do anything but send token military forces.
After brief fighting, the californian republic walks away with all of california including OTL Nevada and the mexican state of sonora.
Texas has taken control of chihuaua, Coahulia, Neuvo Leon and the northern half of tamaulipus
Britain formally recognises The Californian and Texan nations and establishes close economic ties with them. Califonia Buys oregan and the southern portion of Idaho for a token amount in exchange for a garuntee to help settle the NW of OTL Canada in response to increased migration into Russian america (ie alaska)
I don't disagree with your general regionalization of NorAm, but your borders could use some altering. Try starting with a map at the time of your POD and then fill in the blanks from there.