I do remember something from the former Comic Book Resources forum (as it’s been replaced by a new one) that somebody assumed both Barbara Gordon and Barry Allen to be of Scottish descent. At some point I’d prefer the latter to be of Dutch descent (Van Allen/Van Halen) but ended up becoming Irish. (Actually I’d blame my then love of Sinead O’Connor on that.)
So far if The Scottish Connection’s any indication (admittedly I seldom read comics), the only confirmed superhero of Scottish descent’s Batman. Though I could make a good argument for Donald Duck, who despite being an anthropomorphic duck, his uncle and relatives obviously hail directly from Scotland (actually they’re immigrants or expatriates).
Therefore he’s Scottish American. Though for most of the part, it’s not that well-explored so.