Yeah, but then there’s that song they sang while doing it, “as He died to make men holy let us die to make men free”.
About the only thing I can really settle on was the comment by, IIRC, Shelby Foote (what a great Southron accent!), in the Ken Burns documentary. “whatever started it diminishes to insignificance compared to what it accomplished. In a brief four years the pronoun used to refer to the US changed from plural to singular. Globally, universally, and without comment.”. Like he said, it is really quite an amazing thing when you think about it.
Detroit. Baltimore. San Francisco. St. Louis. Atlanta. Washington D.C. The work product of Appomattox.