The very region you chose Dicho, is the one where Native influences most dominated! The OT Banjo method evolved as much from Native American Folk rhythms as it did African American, neither of them vaguely European. To say then that BG is evolved from celtic is the same as saying that because some Bagpiper plays Old Joe clark we must account for celtic as derived from American Folk Music.

So nothing could be more mistaken than to suppose that celtic had anything but a minor influence upon the evolution of American Folk Dance! Bluegrass shares the same heritage so it is likewise accounted for.