I don't know about singing with Scottish accents, but some of those bands listed do have a certain Scottish element to their music, with elements of Scottish folk in it. Mind you, Irish and Scottish folk music were big influences on American music, which in turn has influenced Scottish music... Bands like Big Country and Deacon Blue have a Scottish "sound" to them (in my opinion). And then you get a few bands like Runrig and Mánran, or singers like Julie Fowlis, who sing in Gaelic (some of the time) and who are very Scottish! (although not quite so mass appeal, but they appeal to me!).