If it is, a couple guarantees about it:
1) As is pretty much always the case, the first instances of violence will come from the Left.
2) The Right WILL win, and fairly quickly, for a few reasons:
a) Obviously, we have a lot more guns, and a lot more veterans in our ranks who know how to use them and can teach others to do the same.
b) We have a near- monopoly on food production. Most American agriculture comes from conservative states (Mainly because liberal states have a tendency to drive their farmers to near- bankruptcy with oppressive and often unnecessary environmental regulations, as California did with their "Delta Smelt" lunacy), and one of the first things that would likely happen in the event of a civil war would be for the conservative states to cut off all food delivery to the liberal states. I'd further exacerbate it by broadcasting to the public in the liberal states that we've done this. This'll spark a panic, as the residents of those states will instantly swarm to every grocery store in their states, with every crumb of food bought up or stolen in a day, and eaten in a week. Then, when mass starvation kicks in, the people will start rioting and pressuring their leaders to surrender.
c) We have much more unity in the conservative states than the leftists do in theirs. Many leftist groups and concepts openly clash with each other, such as for instance, the feminists vs. the transgenders (Specifically, that the former of the two groups believe that trans- women are not real women and deeply resent being told they are, and the latter group believes that holding this view is evil and bigoted), the radical environmentalists vs. the labor unions in industries that environmentalists hate (i.e. coal mining, logging, etc.), and the radical Muslims vs. the gay- rights activists (Just look at how leftists look the other way and ignore homophobic violence and persecution when it happens in Islamic nations). These various groups hate each other so much, there is no way they could rally together to actively fight a war, and would likely dissolve into infighting that would further weaken them. While conservatism can have differing groups and factions, they are much better at setting differences aside in the interests of tackling a bigger threat.