No one.
The first Civil War was a sheer stroke of luck in terms of the geographic position of either side. People in the north could go about their normal lives for the most part.
Another one will not be that way.
Anyone acting cocky had better realize that the easy life you enjoy now will come to an end for a real long time if one ever happened.
That is it. Who will be the enemy? Leftists, terrorists, whites against blacks or browns and vice versa, poor against the rich, one political party against the other, bands of roving thugs just out for what they can grab? Americans of every race and culture have lost their mutual identity...we are Americans, first and foremost. Schools and government must instill patriotism again just like reading, writing and arithmetic.