I've started to write a response to this three times, and each time, I've not posted it, and gone away from this thread.

I sympathise with your desire to know more about your ancestors. But I'm somewhat uncomfortable with a subtext that I'm reading, which may not be intended. The subtext is this: that being American is somehow inferior to being Celtic.

My family has been in America for a long time. My earliest ancestor arrived here somewhere in the neighborhood of ten thousand years ago, while the latest arrived more than a century ago. In other words, in the living memory of my family, the only nation we've known is America. For me, this is not a disconnection from my roots -- it is my roots! When I think of who I am, and where I came from, my answers tend to center around Tucson and Arizona.

And I don't think there's anything wrong with that.