You are thinking in conventional terms. If it ever came to civil strife in this country it would be largely irregular or guerrila warfare -- riots in the streets, civil destruction and a breakdown of order and eventually economic activity. The left can be very violent...their roots are in violence but not in the kind of violence that is army on army, in the kind that brought about the French and Russian revolutions. Ask the people of L.A., who have suffered through many riots, whether Democrat voters and consticuencies can be violent!
So much of our vital infrastructure travels right through leftist urban strongholds. Think about the pipelines and railroads and highways which could be cut by sustained insurrection.