I don't find it surprising at all. Our entire nation was founded on the idea of telling the British to fuck off and that we wanted to be our own country. We are taught from kindergarten on that this is a good thing. Why wouldn't we identify with another group of English speaking people who don't want to be ruled by England? (When it comes to people from certain areas around Glasgow I know "English speaking" is a bit of a stretch, but it's close enough for government work.)
Hell, why do you think Americans gave so, so much money to the IRA over the years?
Of course, even if most Americans don't know all the current issues the very idea of independence from England is going to be incredibly appealing for most of them.