The NA communities were certainly 'there' at the birth of the blues, so I wouldn't be surprised if they influenced the development some. But they were very much outnumbered by other ethnic populations that also played a part -- the African-American, of course, and your own Irish countrymen for that matter.

I've long felt there was a definite Celtic component to the blues, especially early, more folk-like songs such as 'Careless Love.' Everyone played a part, most likely, as Marc was pointing out.