Nations of the North
Even though the farmlands of the south have fertile soils that can support all kinds of crops, and long, warm summers, they have their disadvantages as well. The diversity of life down south means more parasites and pests can get into the crops, and a larger variety diseases can infect the populace. Also, much of the American south is rainy and swampy, making it much harder to maintain crops, as well as structures.
North of regions like the Appalachian and the Chesapeake, growing seasons are shorter but the land much more fertile. This means that while there's less of a variety in crop, it can potentially feed a lot more people. It took a while for people to adjust to the bitter northern winters, but once they managed to adapt, very resilient people managed to emerge. The potential for higher, more concentrated populations was needed, because the Yankees live in a relatively more complex society. The soil needs the best medieval technology it can to function, so there needs to be specialized labor forces for ox-breeders and plow makers. The harsher winters mean houses and clothing have to be more elaborate. Stone cutters, lumberjacks and many other more specialized trades are needed to prevent people from freezing or starving to death. However, unlike in Hydraulic Empires, the greater and more diverse groups of people means that these bureaucratic societies aren't as autocratic. There's more compromise and politicking required.
The agriculture of the north supports crops that are much more durable, and are conditioned better to the soils. Cereal grains like wheat and oats are important simply because it's important to have bags of grain ready for the winters, but there's also a large focus on root veg tables like turnips and potatoes. The potato is the staple crop of the North. It is unaffected by snow on the ground, and the starches yield high calories for labor intensive medieval life. Apples, pears, blueberries and cranberries are widely eaten because the trees and bushes can withstand the weather, ready to produce another batch the next year. Because many of the Northern regions are connected to the ocean or the great lakes, there's a large proportion fisherman. Clams, lobsters, cod and bass make up more of the diet of many Northern cultures than meat or poultry.
In the South, structures may be relatively simple due to the common occurring of floods and hurricanes. Aside from the annual blizzards, people in the North really don't have to worry about natural disasters, the priority is in making big, durable abodes that they can all pile in for the winter. Such structures tend to be made of sturdy oak or, if they can afford it, stone. There's a reasonable availability of granite and limestone in some of America's colder regions, so it's very common to build a house with the chimney or hearth being part of the entire wall. The use of stone is valued not only for the insulation from the hot summers and cold winters, but because firewood may burning for so much of the year, there's a higher risk for flammability.
The Northeast of the US is not blessed with much unique resources. Just a great deal of wood. However, the cash crops of the South and the minerals of the farther North, as well as the seas and rivers create trade network that cities can sprout up on. Also, because people of the North want to concentrate on exporting rather than importing, trades in artisanship are very important. In order to stay competitive with the relatively little they're given, these places make it a point to be the best as textiles, metal-working and wood crafting that they can be.
Perhaps what the Yankees pride themselves most on is their scholarly pursuits. With so many Church districts nearby, a much higher proportion of the populace is well educated. Churchmen are often hired, not just to do many of the bureaucratic work, but tutor the children of the region's leaders. Many prestigious colleges of old were located here in the industrial age, and while some fell into disrepair, it was considered very important to keep the tradition of learning alive. While many of the kingdoms further south and west have no interest in enrolling their sons there for fear of going soft, the occasional kingdom (Usually in peacetime) will send important scions to Universities in the Northeast in the hopes of having a wise and well-versed leader succeeding them.