The Northeast

We'll start our exploration of Medieval America here. This is the site of some of the earliest settlements by Europeans, and nine of the original 13 colonies. It was where two of the four largest cities of the country were, and the source of a thick urban corridor which defined modern America. So we have both a model of pre-Industrialization, and post-Industrialization, to really get a good idea on how much this world has changed. 

The Northeast is still probably the most urbanized region in North America, despite its status being greatly  diminished. This is probably because of continuity--many of the oldest municipalities, were designed for a population before automobiles, and organizations would have precedence for a de-industrialized way of life. The bays and islands also help a great deal in maintaining a maritime culture, which are also historically more city-based.

We have an icon of a plow that leads to "Yankees". This would be the lifestyle for those who dwell in the north, but what does that indicate? Looking at  Southern Farmers, this would largely mean Americans who live in the green, under six month area (not including the areas that are colder due to higher elevations). When you look at this map , a lot of the most arable soil tends to fall in the that line. So a people that can be well fed, but they have to work hard to for it, and probably reserve most of their downtime for the winter. Funny enough, White makes no mention of potatoes. It's possible he neglected them, or even planned a potato blight because 1) He wanted Northerners to strictly eat Old World foods, or 2) He considered the potatoes to be a bit of a game breaker. White didn't have an image of the Yankees in his cachet like he did for Southerners and Herdsmen, but that's probably because they dress pretty similarly to Medieval Europeans. The Northeast isn't lousy with natural resources, so they focus on crafting finished goods.

However, the "Yankee" Notheast culture isn't completely defined by the climate. After all, this include Maryland, which is below the Mason Dixon line, and even New Jersey can be pretty warm.
That's because something that defines The Northeast, that separates it from the Feudal Core, is the sense of Republicanism. The U.S. remains a republic, probably more out of inertia/want for retaining power, but a republic it remains nonetheless. Maryland also has two other aspects that makes it part of the overarching Northeast culture, despite having more in common with the tidewater south. The first that, as it's basically split by the Chesapeake Bay, it's developed a nautical culture that's very distinct from the warlords out west. (Though they do appear to have knights). The second is that it's home of the headquarters of the Non-Denominational Church, and as former state capitals tend to serve as district headquarters, and Northeast states are small, and their capitals fairly close to each other, this means the Church has more of a say that military strongmen. What effect does this have in the region?

If you combine a mentality that is shaped by Puritans, Quakers, and Dutch merchants, it means a society that is somewhat ascetic, but charitable and not focused on class differences.  It should be said that that more church HQ's and a bookmaking industry might turn the Northeast into the new Bible Belt. It's not that the Northeast is necessarily more religious, it's just there are more physical bibles per capita.

White has already covered what has happened to the federal remains of United States. I won't get into too much, but it look two cities it's definitely taken over are New York and New Haven. It's also absorbed the bays of Rhode Island and Massachusetts, but it's unsure how much.

New England has broken down a little bit, with ten or so states where once there was six. The borders seem to gravitate towards a more circular shape when possible, and similarity in size, as opposed to the rectangular states of old New England. They conduct their government as republics, not as expansive sea-faring empires, but likely as collections of towns and villages with town councils dating back to colonial times. There's a lot of Church supervisors, but no major cities, except for Boston and Providence. Both are located in Massachusetts, which is the big dog of New England, and is the only country with its own map. Well, they may be located in Massachusetts--they border the territory of the U.S. As this map may hint at, there's something of a fight going on in this area, and maybe those two cities are constantly fought over. Or maybe Massachusetts is a client state of the U.S., and it operates like a colony, much as it did when it was first founded. In general, New England operates as pure, distilled, Yankee culture.

And then we have New Jersey. It includes the historical state borders, but also extends into Philadelphia. As this trade map shows it's possibly the breadbasket for much of the Northeast territories, and being more agrarian than its  neighbors may be why it's a feudal state. I also have a theory that a few Mafiaos have taken over at some point, and the Mafia has always had something resembling a feudal order. Still, it's probably more mercantile than the kingdoms in the Heartland, and curiously, it looks like they prefer to use pikes to cavalry, which is a bit of an outlier. The rule of thumb is that pikemen are more popular in Republics, (though it also seems to be popular in the Appalachians for easy to see reasons) and knights in the feudal territories. It's possible that while much of the Northeast fancies itself the heir to the Classical World, New Jersey is the region's answer to Sparta or Macedon.