I gotta agree with Weapon_R on this one. It's not just trade, and the lack of an Atlantic port, it's also the loss of face in the political and economic community. How well does it reflect on our bargaining power, if we can't keep our country together? And as for our supposed (and often trumpeted) superiority to the Americans... well, we'd never hear the end of it.
The Czechs and Slovaks managed to separate amicably in '93, but I can't help feeling like they got off lucky.
"Oh yeah! Plus, armed men are stealing my pop!"