It's all relative. I still recall having to go back east for corporate training and encountering fellow underwriters from every branch in New York. Where those from Buffalo and Rochester spoke much like most folks out west. But then the people from different boroughs of New York City....I practically needed a phrasebook to keep up with them. And how I found talking to other employees from Alabama, SC and Texas just seemed comforting. And dealing with people in central city of Philly could be quite amusing too. Hearing all about "Youze guys".
I used to always laugh watching actor Barry Morse portray a Brit in the tv series "Space 1999". Until many years later I learned that Barry Morse WAS British. I always hated the infamous Lieutenant Gerard in "The Fugitive", but I never gave any thought to him being a foreigner! Oops.
Frankly these days with so much excellent and formal coaching, a lot of actors can be trained to effectively sound like someone they aren't. Like uber-skilled actors Daniel Day Lewis, Charlize Theron or Cate Blanchett who can convincingly play just about anyone from anywhere. Remember "Addy" from "Z Nation"? She's Russian. Some can deliver the goods, others can't.
Though on occasion I have seen actors like Mark Rylance who was supposed to portray a Soviet covert operative in New York skillfully extracting atomic bomb secrets in America. (Bridge of Spies) He sounded neither like an American or a Russian, with his Scottish accent continually popping up. The again I suppose the Scots would probably have had a bone to pick with Star Trek's Canadian James Doohan as well. And watching Monty Python's Graham Chapman struggle to do a terrible American accent....priceless. And then there were like Richard Burton, James Mason and Peter Firth who embarrassingly attempted to portray Southerners. Ouch.
American television and film is a very lucrative industry. Attracting all kinds of talent well beyond our borders. Whether English is or isn't their first language.
Still, it might be amusing to have some up-and-coming actor skillfully doing various accents to be asked by the press how they do it. Imagine an actor lamenting that it simply involved a blow to the head.
