Stop for a moment and examine the military conflicts our country has engaged in since WWII. Even though we've possessed the might to break the back of any enemy, we've tread lightly, pulling our punches and allowing these conflicts to stretch out interminably. We haven't decisively 'won' a conflict since 1945. Why?
It's because our people and our political leaders are risk averse and unwilling to unleash the full horror of violence we're capable of. As I've said, we no longer have the stomach for brutally crushing others through force - especially over mere political disagreements.
It's hard enough for a President to get the support to send our military against an organized and militant foe who presents a real threat to our national security, let alone, one who presents NO threat whatsoever.
One or several states seeking peaceful separation from the union present no military threat to the rest of the country. It could be argued that their leaving the union would constitute a threat to national security, but that's a hard sell when you're trying to make the case for the use of military force to compel those people to remain in the union over their objections.
We also have to remember that political union is a state of mind. When the people of a country become as divided and distant as they are in America today, only legal entanglements hold them together. Frankly, there's a huge portion of my countrymen whom I do not love. And they feel exactly the same towards me. Who's to say that they wouldn't celebrate my leaving? I'll bet you most liberals would be ecstatic if the red states chose to secede.
An attempt to order our military to violently crush a secessionist movement would also likely backfire on any CIC who tried it. He'd be asking Americans to fire on their own people, which would create immediate and disastrous effects up and down the chain of command. Such an order would cleave the military in two, and could even result in the arrest that President and his chief lieutenants.
A state or states can be as peaceful as the want about leaving but I’m telling you that whatever asshole is sitting in the oval office is going to see that as his/her moment to be held up in history as the next Lincoln and will spill as much blood as needed to bring a rebel state back under control. You think brutal things like the NY draft riots and Sherman’s march to the sea have been bred out of us just because it’s 2013?