The states formed a Union under the Articles of Confederation in 1777. It continued in effect until 1789 when the government established under the Constitution started operations.
The Constitutional Convention was quite explicitly established to suggest modifications to the Articles that would help its government function more effectively. So at the time the Constitutional Convention was held, the states had not been independent for 10 years.
Uh... that wasn’t a union. It was a confederation. Words have meaning. And the way you used them in your previous posts to me do not apply to the last one. You can just make stuff up as you go along. Go to a liberal web site for that.