The American Civil War took place for many reasons, but what allowed such a situation to arise was geographic concentration of economics. The 13 States that all seceded from the Union were geographically connected and were all agriculturally based economies that relied on the labor of African slaves. The "Union" states were all industrial manufacturing based economies.
What you see going on in the United States now is ideology bases opposition that is not geographically isolated. Urban areas with high poverty are in every state of the union. Think of a polka dot pattern. Opposing ideologies also do not have equal amounts of monetary resources, military equipment, or private citizens willing to risk their lives in a shooting war.