There’s some key questions that need to be answered, for the setting to make any sense. We know that the US is (in 2039) fractured. There are six major polities, which govern only part of the country, and even those which are nominally part of the same polity (the Fed) are effectively different nations.
But why? Why is the United States so fractured? The answer is simple: it’s all down to tribes.
Humans are tribalistic. It’s innate, evolutionary, necessary to survive. We divide the world into Us and Them and (in most cases) hate and fear the Them. (Whoever the “Them” are.)
When two foreign tribes come into contact, 99% percent of the time the absolute best you can expect, the pinnacle of morality and decency, is benign indifference. They interact, usually trade, and go on their way. A step down is suspicion and distrust. Below that is active hostility and below that, killing. Two tribes who compete for the same resources will become enemies, and enemies, sooner or later, will kill each other. This is tribalism.
(I note that benign indifference isn’t immoral behavior. When survival is a hard-won prize, when every day is spent on the edge of starvation, disease, or death, there is no generosity, because there is nothing to be generous with. The widow may have donated her two mites, but if there are no mites, have never been any mites, and will never be any mites, not for centuries, people give nothing because they have nothing to give. Generosity is a virtue of those who have something to be generous with.)
America, in 2039, is tribalized. It is broken into thousands of tribes, dozens of multi-tribal alliances, and six small nations.
Each settlement is a separate tribe, unto itself. Each city-state is a strong tribal alliance, each local or regional confederacy a weak one. Each of the six polities are (in effect) small nations, and they view the others as foreign and strange.
New York’s urban warriors and agro-businessmen have little in common with the optimistic industrial laborers of the Dakotas or the devout but impoverished farmers of Utah. They see the world in different ways, have different customs, morals, and social norms, and are deeply suspicious of the “other”.
America has regressed — it is no longer one nation. And 2016 is why.