Early this morning, I finished a project I had undertaken nine months ago: compiling the hymns from a number of American Lutheran hymnals. Praise the Lord! I cross-referenced all the hymns from the LCMS, ALC/ELCA, and ELS. The document ended at 49 pages.
I haven't done a detailed analysis of the hymn traditions between American Lutherans, but I did note that some hymns appear in every (or nearly every) hymnal. Obviously, "A Mighty Fortress" would be one of those hymns. I found also that you can visually see a hymn's genealogy among the LCMS and ELCA. Each of these synods has a very definite core of hymns unique to their history. It is also interesting to see what hymns were in early hymnals, but were dropped from later ones.
Now I can pick up in earnest my other hymnal project: translating untranslated hymns from Synod's German hymnal (i.e. those German hymns that never made it into our English hymnals).