I believe one thing the article greatly over-estimates is the loyalty people have to States, especially among younger generations. Even here in Texas, which has a very unique identity for folks from here (we already think of ourselves as another country; younger generations don't see it that way).
Even if the States initially split up as described here, they would immediately become internally factioned with other groups people are more loyal to: religious, political, various identity groups. You would also have charismatic leaders from a wide range of backgrounds bringing people together. Dixie rising again would be replaced by the Southern Baptist Union. California would rip down her spine into separate entities which long didn't identify with each other. Texas would faction with the South West part of the State, largely Hispanic joining with other highly Hispanic areas of the country as a La Familia union. Eastern Texas, if more identifies with the deep South and would be taken in rather quickly by the Southern Baptist Union. The panhandle would split off and join the grain belt of Oklahoma, Kansas, and Nebraska, instead of fighting their neighbors, profiting and selling food to whomever pays for protection. Much of the North East rural areas will isolate itself while large cities like New York and Philadelphia would become city-states using whatever resources it has to try to buy protection for as long as it could.
You would most likely have charismatic leaders rising in major areas, some offering religious salvation on a mass scale, others trying to be warlords. The 90% of the population that doesn't want to fight (fear, lack of skill, or lack of desire) would follow whomever seemed the strongest and gathered the most to him.
But when the war goes hot, it won't last long. You wouldn't need an EMP to cripple the electrical system. With the country already factioned like this, power, water, and food supplies would be held together with threads of trust and payments. One or two strategically placed attacks could cripple the power grid for the entire Eastern seaboard. California could be cut off from water quickly. Las Vegas could be shut down in a few days by cutting off its water supply, as would Phoenix.
Oil refineries are very easy targets and we can expect some sort of early attack to cripple them. It may not even be from one of the factions, but a lone eco-terrorist who believes he can change the world, in the dark of the night, with a small explosive can do a lot of harm.
One of the biggest battles won't even be for land, it will be for information. Who can control not only the media (centered in 4-5 major hubs) but also the backbone of the internet. The latter controls so much, a disruption could cripple supply chains faster than bombs could.
And of course, one has to consider foreign intervention. Immediately after the split, just like in the time of our Revolution and Civil War, the various factions will reach out to countries for support and partnership. Canada could end up becoming a strategic partner with States from Michigan to Maine, creating a dotted line border and a new protectorate. Mexico would partner with La Familia from SW Texas to Southern California. Europe would see quick partners with the Gulf to the East Coast. China, no doubt, would swallow California in influence quickly.
It would be over far faster than is written here. Those who dream of their own personal revolution or civil war, taking pot shots at the enemy with their old hunting rifle will be greatly disappointed. It will be a cold war built mostly on negotiation and very, very strategic action, not a large scale hot war.
