The notion that the Union was not perpetual did not even occur to anyone until the 1830s, when pro-slavery politicians invented a supposed constitutional right of a state to secede.
"We the Delegates of the People of Virginia duly elected in pursuance of a recommendation from the General Assembly and now met in Convention having fully and freely investigated and discussed the proceedings of the Federal Convention and being prepared as well as the most mature deliberation hath enabled us to decide thereon Do in the name and in behalf of the People of Virginia declare and make known that the powers granted under the Constitution being derived from the People of the United States may be resumed by them whensoever the same shall be perverted to their injury or oppression and that every power not granted thereby remains with them and at their will[.]"