If Texas seceded, would the other states of the old Confederacy do likewise, except Virginia and Florida, but plus West Virginia, Kentucky, and Missouri? Also, would the Plains states north of Texas (Oklahoma to North Dakota) do likewise, along with the upper Rocky Mountain states of Idaho, Montana, Wyoming, and Utah? The states can then form a confederation using the Articles of Confederation as a guide. They can then encourage adjacent conservative areas in non-seceding states to form new states. For example, the southern one-third of Ohio, Indiana, and Illinois, northern Florida, eastern New Mexico, most of Nevada, eastern Washington and Oregon, western Maryland, northern Colorado, Piedmont and Appalachian Virginia, and western and southern Iowa. Unfortunately, conservative areas in Arizona, Pennsylvania, California, and Wisconsin are too indefensible to hold against a rump United States.
The members of the new confederation would then be Christian, free market, and traditional societies, while the states of the rump United States would become fully social democratic, secular societies on the European model.
The states can then form a confederation using the Articles of Confederation as a guide. If the U.S. splits up you assume it will be into two pieces. Why not three pieces? Or four? Texas may combine with the the old confederacy, but I can easily see the blue states of the plains and the northern tier creating their own country and doing quite well. That would leave the Northeast and the West Coast, and they may go their own way, too. Where you once had one country you would probably wind up with at least four.