Need I remind you how the last civil war went?
The west and the north east will be ready to fight, and we have plenty of military bases, equipment, infrastructure, logistics, money and people to fight with. The neo-confederate rednecks will be cut off from trade in every direction, as we quickly take both coasts and form alliances with allied countries (not just Canada and Mexico, but also Europe, Japan, and South Korea, who will need to continue trading with coastal American states).
All the 400 lb good ol’ boy mall ninja rednecks in the world are not going to be able to face the reality of what will come to them if they fuck with the west coast. People in Buttfuck, Oklahoma will be eating dust off the ground in the dark by the time we are done with them. And this time there will be no forgiveness or reconstruction.
We take the Pacific and Atlantic coasts first, blockade the gulf and then move inwards with our allies from all sides.