But fake American accents predominate almost exclusively in western popular music.
Maybe in mainstream ‘pop’ music, which is basically trying to appeal to a global, (read ‘American’ market), but listen to indy, folk/roots stuff, and you’ll clearly hear regional accents. Even bigger bands, like Elbow, you can hear Guy’s Mancunian accent, but someone like Jake Bugg, Luke Sital-Singh, Billy Bragg, Kate Rusby, Mary Epworth, Rae Morris, Royal Blood, Belle and Sebastian, The Amazing Snakeheads, you can clearly hear an English or Scottish accent, usually regional.