You often see this irish/Scottish origin for oldtime and bluegrass being asserted, but what actual evidence is there. I would have thought English traditional music would have been equally(at least) important. The handful of old world tunes that survived moderately intact in the American fiddle tradition seem as likely to be English as not, or at least the ones I've seen mentioned seem to be. Not that it is at all easy to define a tune as English or Scottish or whatever.
And while Bill Monroe's family was of Scottish extraction, I believe, that doesnt apply to the majority of oldtime musicians, does it? For example, if you go through lists of oldtime musicians you dont get a strong impression of a preonderance of Irish or Scottish names.