A very important point of consideration.
Prior to the Civil War, it was usual to refer to "these" United States. There was a clear implication that there were many states and that they were (in effect) on the same team.
Since the Civil War, we use the term "the" United States, implying that there is a single political entity and we all participate in it.
There is a very important distinction there.
Prior to, and during, the ACW many people were very clear that they cared only about their state. They were citizes of, let's say, Virginia. They fought for Virginia. If Virginia had an agreement to be in a union with NY, fine. If Virginia did not have an agreement to be in a union with NY (and MA, and CT, and ...) then that was OK too. The key fact was that the citizen was a citizen of Virginia.
The modern sensibility that we are all expected to grow up with is that the United States is the only thing that really matters and we are all citizens of the USA. It is vital to realize that this is an idea imposed on us all AFTER the Civil War and BECAUSE of the Civil War.
Such an ideology cannot be used to counteract the thinking of people prior to the Civil War on why they should be free to leave the union of the several states. They simply didn't think the way we think now.
This was the point that I was trying to ram home. We are not merely citizens of the United States, but citizens of these United States and Commonwealths.
You cannot be a citizen of the United States without being a citizen of one of those States first.