I'm naturally skeptical that any state, even Texas, could successfully make a go on its own. However, if several red states get together, especially those more rural populations and with commodities that are easy to trade on the world market (read O-I-L, as in many red states), then there may be a path.
And the obvious spark would be an economic collapse: many blue states would gratefully accept the chains of communism, whereas the hard-red states would be tempted to refuse more of the same medicine known to be a poison. In the event of a collapse, the Federal government may not have the resources to enforce a union. Let me note that there are millions upon millions of firearms in private hands in the United States, with billions of rounds of ammo.
It's unlikely, but we're utterly off-the-charts in terms of economics, so it's not impossible, in my opinion. When times get ugly, ideas that were once considered bizarre come to the fore.
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