Because American and British are the only people that matter in the world? Is that the point you are trying to make?
I believe what he means is "native English speaking". People who don't speak English as their first language tend to have more noticable accents than countries where English is the first language; probably because we become accustomed to hearing English and American accents as they are common in our daily lives and media - Try listening to a white South African and you'll find they also sound "foreign" even though English IS their first language, lack of familiarity at work.
Now stop trying to make a strawman and flog it
Cockney? You sure you're a Brit lol? Stephen Merchant's got a VERY West Country accent! It's not Cockney at all!
I'm Cornish >_> - Thought it sounded like one of those funny London accents to my ear... can never keep straight which is which. That said EVERYONE is a northerner to me xD
Edit: Yeah listening to a clip of him again not sure why I got the impression it was a london accent, it's south west. Just show how long I've been living outside the country. Point still stands though... british accents = automatic villain ball.