The default singing accent in pop music is American. And for a reason. Had the band Tears for Fears sung 'Mad World' in a Scottish accent it would have been quite a different song. Instead of a soul-search for the meaning of life, it would have been about a sewage engineer trying to sort out a pipe blockage (see the clip at http://www.tinybangtheories.com/2012/01/familiar-faeces.html).
Best wishes,
Paul Angliss (Ed.)