Even though we have "Red" states and "Blue" states, or terms like "flyover America," we are too intermingled to ever have a successful secession.
Whether it's NY, CA, AZ or TX, there are dirty unwashed hippies, illegal immigrants, bitter-clingers and Paulians intermingled together in various percentages.
A second Civil War would probably end up as a war of attrition, coming close to a form of political genocide or purging. It would then draw the UN to come and "keep the peace" on top of it all, further pissing off the bitter-clingers and Paulians to protract this war of attrition.
The US could Balkanize after a couple years of this. I know that if things began moving that direction in AZ, I would move elsewhere. If the FedGov won't get behind border security soon, AZ will be another Mexican province in maybe 10 years. I think there's between 1.5 and 2 million illegals just in my state.