Why on earth would the Dakotas want to sign on to being the tail end of some new country dominated by Texas or the Southeast? Why subjugate themselves to Atlanta or Birmingham or Dallas or some other far away capital? Wouldn't independence or the formation of some nation of truly "like-minded" Great Plains states be preferable?
And really, by this point Virginia and North Carolina and Florida wouldn't fit in very well to some new Confederacy. Even Texas would be divided. Almost every state has at least a 40% minority that votes for the party that didn't carry the state in the presidential election. It's not like 1860 when Lincoln and the Republicans got no votes in the Deep South states. There's a large enough group in every state that fears what would happen if the more extreme of their neighbors got their own way.
The economic might alone will leave liberal cesspools like California, Massachusetts and New York relegated to even more of a third world status than they already are.
Surely some parts of the country are closer to "third world status." I could see San Francisco or New York City arrogantly cutting themselves off from the rest of the country before they'd sink into the kind of poverty you see in other places.
Some parts of the South and the Heartland, though, could be really hurt by leaving the US economy. Why would the Japanese make cars in Tennessee or Mississippi or Alabama if the domestic market where they could be sold is cut in half and the political situation turns unstable?
What? Both of those cities are already mired deep into third world cesspool status. In particular, San Francisco's long history of hippies and homosexuals had reduced an entire region to unhinged ultra-liberalism which translates to confiscatory taxes and burdensome regulations, driving productive people to more welcoming places elsewhere in search of liberty, prosperity and the entrepreneurial spirit.
As for New York City, that socialist-run city is best summed up by native Texan Buck Owens' song: I Wouldn't Live In New York City. In a similar vein, Conservative Patriot Hank Williams, Jr. succinctly summarizes things up in his unforgettable standard: Dixie on My Mind.