One major problem.... well..... two major problems.
One: The so called "left" most likely outnumbers the truly right wing states. Most of the most densely populated cities and states are located in liberal strongholds.
Two: Those same cities and states will have waaaaaaaaaaaaaaaaaay more money than the cities and states in the south and the flyover states.
Not much has changed since the first civil war. The south had superior generals, they had soldiers who grew up in an environment that lended itself to warfare (gun culture, etc) but the North won. Why? Economy. They could simply outproduce the south. They had more industry. It's the same reason why we beat the Germans in WWII. They had superior technology. We just outproduced them. That's how we win wars.
So yes, the south has more gun owners, and more people that can shoot, but in a war of attrition they're going to lose. They will be painted as extremists. As racists. As bigots and religious zealots. The moderates and the liberals will band together.
http://abcnews.go.com/Politics/trumps-approval-rate-time-low-slip-support-base/story?id=49015043
Trump currently has a 33% approval rating among registered voters, and conversely he has a 61% DISAPPROVAL rating. I don't think their "civil war 2.0" will gain as much momentum as they think.