Yep. If the civil war happens, rival militias will be taking pot shots at each other. The economy will be disrupted. But fields will still grow wheat, factories will still make cars, and offices will still move money around. Most Americans will learn to keep their heads low and run the other way when bullets are flying. There will be innocent bystanders, but USA will not become a Mad Max world.

The next question should be: "Where does the USA go after the belligents are killed off or come to some kind of sanity?"