Puerto Rico and other terroritories might become states in the future.
The Southern states were part of the USA, so they couldn't secede. In which part of the Constitution can you read about the right to secede?
"Puerto Rico and other terroritories might become states in the future."
I meant "territories".
Wrong document. Check the "Declaration of Independence."
Based on that document, there is indeed a fundamental human right to dissolve the bonds that bind a people to an unjust government. Whether or not the confederacy accurately represents such a case is open to question; but the existence of the principle itself is not.
Or would you say that the Declaration is erroneous on that point?