The Union was like a balloon and it is no longer a Union if you can unilaterally leave it. That is a mere Confederation which the Constitution rose above. But even that document stated the Union was perpetual.
I can’t believe you believe the Civil War was of the same nature as the Revolution. Of all the weak, vacuous arguments that is the most weak and vacuous. There was no union in GB it was a KINGDOM; no colony had joined the Kingdom voluntarily. None had any representation in Parliament. Not only did the Southern states have representation they had controlled the government until Lincoln and the Republicans came on the scene.
We left the Union of the Crowns. It remained a Union after we left it. Our justification for leaving it was the natural law assertion that people have a right to independence from a government they felt no longer served their interest.
There was no union in GB it was a KINGDOM
It's proper name is the "United Kingdom." It was created by the Union of the Crowns, and it was in fact a Union.
Now if you are arguing that the United Kingdom was an "involuntary" Union, then I will point out that ours started out as a voluntary Union, but after "Four score and seven years" it certainly ended up as an involuntary Union.