Marianne, I shall have to defer to your greater knowledge on this. I have to confess, I know little about the issue! But I am interested by the asymmetrical intelligiblity between English accents. Whilst Geordie folk have no trouble understanding American English (thanks to the constant exposure through the media), I doubt the same can be said the other way around!
Yes, seems the exposure doesn’t happen so much the other way round British dialects to American listeners. I’ve seen TV/films intended for american viewers, with subtitles for either english dialect accents, or even southern american accents, and ebonics that wasn’t too heavy.
Regardless of language, I think everybody understand the accent(s) they encounter in media. A “standard accent” or “high variety” is usually understood by anyone (as well as the one that 2nd language learners are encouraged to study). All this RP, High German, rikssvenska, Castillian distinción, General American, MSA… No wonder people from the other side of the pond has an easier time understanding these major varieties than rural. Anybody have heard Americans. Not everybody have heard Geordies.
On-topic: Interesting BBC interview!
Jeff - Does your assumption not presuppose that Americans do no possess the many varied accents you might find in the UK?
I guess they would also have their geordie variants.
@david machin - I am sure you are not interested, but I will say it anyway. It is unlike a network such as Fox did not notice the geordie accent at the interview stage and that this did not flag up as a potential problem 
Of course there are varieties in American English, but maybe not as many (or as distinctive) as in the UK. Or rather, many American accents (no matter how distinctive) are featured in just about every movie/TV series. I think I hear General American, Southern accent, Ebonics and maybe the “gangster accent” nearly everyday, and that’s here in Sweden.
In another thread at HTLAL I wrote:
“Some people I know” tend to judge accents in movies according to this:
*non-rhotic accent - British
*non-rhotic + glottal stops - Cockney
*rhotic tap - Scottish
*non-rhotic + high-rising terminal - Australian
*rhotic tap/alveolar + high rising terminal - Irish
*rhotic - American/Canadian
*“rural” British English (for lack of better description) - usually Irish/Scottish
Not that the above is close to the truth but that’s about how some people I know judge spoken English in movies.
I’ve heard people shout “Wow, that’s Irish!” (or Scottish) at any random British film or TV series where the actors didn’t sound exactly like Hugh Grant, e.g. Emerdale Farm, Billy Elliott, Brassed Off, Bend it like Beckham, anything by Ken Loach and the list goes on.
What would be the American “Geordie” equivalent?