I just finished the whole series. I liked it better than the Rawles books. It was kind of expensive to read them all was my only gripe, but I would do it again.
I could definitely see a split up of states similar to what he described. I also hope the percent of our military that would not take arms up against fellow citizens is accurate in real life versus the book.
When I was studying some of this stuff a long time ago, one of the "rules" for writing is that no matter how hard you try you will incorporate your "present time frame as of the date you are writing" into the story.
For instance, I think in Earth Abides, there is reference to the "new class of drugs called antibiotics" and the "new drug penicillin". In one of the "Die Hard" movies, Bruce Willis refers to the "Glock 7 ceramic pistol that can pass thru an airport metal detector without being seen and costs a year's salary"
In the 299 days series, the refer to the use of ammunition as currency and to .22LR as "change" for this form of currency much like a penny is change for a dollar because .22 is so plentiful and cheap.