Secession is very possible. The war may or may not happen. I think the USA would be happy to get rid of as many red states as possible without bloodshed.
But then where would they find the large middle class tax base to milk for social programmes and ill-conceived foreign wars?
Secession won't happen because we're not a red state/blue state country. We're a red rural/blue urban/purple suburban country.
One detail that I found interesting in this article was choking the cities by preventing the delivery of food. Seems this would be very easy to do and like the article stated, most Americans are only about 9 meals away from not having anything to eat.
Another detail I fund interesting is that it won't be a simple, 2-sided conservative/liberal civil war. It'll be a whole bunch of armed groups that cross the political spectrum all vying for power.