The yanks have it easy writes Rebecca Schuman:

• British actors can do great American accents (both Christian Bale and Henry Cavill – the quintessential American heroes, Batman and Superman – are actually British) but the opposite isn’t quite true.
• This is in part because if aspiring British actors want to make it big; they have to be able to appeal to Hollywood and the massive American market.
• The Brits have more of a tradition of actors being formally trained in the art of theater – including dialects. Americans often pick it up as they go along.
• Great Britain with all of its history also has more diversity in accents than America, despite the size of the United States. The British thus learn to adapt early on to different speaking styles.

Read the full article on Slate.