As a former US history teacher, I don't see how you can just start with the Civil War without giving the constitutional/political background on the slavery issue and states' rights. I assume you do not just start with the election of Lincoln.
I teach American History in a two semester sequence. Discovery & Colonization to the War of Northern Aggression in the first and Reconstruction to 20th century in the second.
We spend two solid weeks on the Constitution alon, AFTER a good background in the Enlightenment.