Of course, this often isn't true, as accents within Britain and America vary so widely. New York and Boston accents, for example, have a flat "r" sound, while Cornish, Scottish and some West Midlands accents are among those in the British Isles to retain the rhotic "r".
So which is the most common English accent?
English is spoken worldwide by around 840 million people, and is the third most-spoken global language after Mandarin Chinese and Spanish. It's the mother tongue of 335 million people, and a second language for a further 505 million. As most English speakers don't speak the language natively, that means the most common English accent in the world is probably what is known officially, if imprecisely, as "international English".
So for some Sunday entertainment I thought I'd share the song – “You say tomato, I say tomato” – which defines the major differences and in which we supposedly agree to call the whole thing off... being half American, half British this is the story of my life!