A little dust up in the 1860s established the precedent that states cannot leave the union unilaterally.

However, there is a little-known (and intentionally not discussed) pathway within the constitution itself to dissolve the union and allow the 50 states to each go their own way.

Article 5 includes a provision that allows 2/3 of the state legislatures to call a constitutional convention; neither the US congress, nor the Prez, nor the Supremes would have any say in this and would be powerless to stop it.

Once a constitutional convention is called, anything is fair game in terms of the amendments that can be proposed. They could even propose an amendment that would effecively terminate the constitution and dissolve the union.

Once such an amendment was proposed to the states, if it were ratified by 3/4 of the states it would become effective. Again, all three branches of the US government are completely bypassed, and are completely powerless to stop it.

There is actually a very good legal precedent for this: the constitutional convention that drafted the present constitution. It was called for the purpose of amending the old Articles of Confederation. It instead proposed scrapping the old Articles and doing something completely different. This is exactly why the delegates to that convention wrote Article 5 the way they did - they wanted to leave open the possibility of doing it again.

Hardly anyone knows about this. It is deliberately not taught in the schools or mentioned in the MSM or by any government official, for obvious reasons. State governors and state legislators probably do know it, though. Should the federal government ever get to the point that it is nothing but dead weight and more trouble than it is worth, you might be surprised how quickly this could all happen. The USA could be dissolved just about as quickly, and just about as surprisingly, as the USSR was.