It looks like New England is getting along with the British swimmingly, though I'm surprised and impressed that they were able to set up both a merchant marine fleet and vessels capable of patrolling alongside the British.
For shits and giggles, imagine the British sells Nova Scotia to New England, and then a new territory named New Cambria gets added to the Commonwealth. You'd have the "Commonwealth of the New Britain", made up of New England, New Scotland, and New Wales.
From your hints about a possible War of Reunification starring Andrew Jackson and the recent developments in New England and Mexico, it sounds like it would go terribly for the US.
Speaking of terrible. We have a country, which was posed to be the next regional power on their continent, lose a war of aggression, lose a decent portion of their land which was split into new countries, had their economy is going down the toilet, all while nationalism and revanchist sentiment is brewing.
It's a good thing that the US is no where near industrialized enough to be able to wage a mechanised war on all of its neighbors at the same time.
I hope that the new Mexican emperor can help modernize the country, form a strong military, and can fortify its borders or it will be the first victim of "Manifest Destiny".
Edit:
It's always great to see an update from you. Hope to read more.
