Is there a several-paragraph or so summary of this TL? It looks quite interesting (in a train wreck sort of way), but the length of it is rather daunting.
Jefferson dies of a stroke during a sensitive part of his second term, his VP is worthless, and as a result the northern parts of the union form the Federal Republic of New England. While it renders any sort of Fugitive Slave Act null and void, it also leaves so few abolitionists within the "USA" that chattel slavery is never banned. The *USA conquers Mexico and adds debt-peonage to its list of legally codified castes, is on the winning side of *World War One, but has become an international pariah for its continued advocacy of slavery. I stopped reading about the time Jared was shaping up WWII, so it's probably continued since then.