I'd imagine that most white Americans are a conglomerate of just about everything European. My ancestors have been here since colonial times, plenty of time to mix it all up.
I went to a Scottish festival a couple months ago and was impressed enough to wish I had some Scottish heritage. I mentioned the event to relatives during my Christmas trip, and it turns out there's some Scottish on my mother's side of the family. (Her maiden name is one of those Scottish names that's had the "Mc" taken off the beginning and its spelling slightly changed. I didn't even notice that until it was pointed out to me.)