This isn't 1861. Americans no longer have the stomach to murder millions of their fellow citizens over a matter of political union, and there will be no public support for any regime that attempts to use our military for such overt suppression.
People do not change. Human nature is the same now as it was in 1861, or 1775 or the day that that Cain slew Abel, for that matter. Faced with the imminent loss of power (and probably the means of food and energy production) the Federal government will put boots on the ground in your hometown faster than you can say "Abraham Lincoln". And all it takes to force a soldier to obey any order is put another soldier behind him with orders to shoot him if he hesitates. It worked for the Soviets, and it would work for Barack.
I don't have the least doubt that there would be lots of support. Certain groups, and there are many, would be pleased as punch to see Obeyme wipe out city blocks full of "domestic terrorists" like us.