from my experience as a Canadian who lived in the UK for 2 years, it's much harder for a North American to do a correct English/Scotch/etc. accent than vice versa. the two reasons I believe that make this the case is A) British people have great exposure to Hollywood films and can watch them without dubs, therefore making it easier to pick up for them and B) the UK has an insane amount of accents. Someone from York will sound entirely different than someone from London than someone from Birmingham, or Edinburgh etc., and social class also has a profound impact on the accent that one uses in the UK. In NA, there are slight regional variations on accents, but, with the exception of the south and maybe New England, all sound relatively similar and employ similar phonetic trends.
I think your B point is a common misconception. There are a wide array of accents all over the American South, alone, and UK actors are often terrible at them. Many great and popular Canadian actors are pretty terrible at American accents too. Listen to a Jim Carrey or a Michael J. Fox's rampant "soreys" and other obvious giveaways. Marty McFly is supposed to have roots in his small California hometown going back to the 19th century.
Wonder how Peele's 'success' as a director ("Get Out") will affect their (Key & Peele's) chemistry going forward (though given the fact that the 'main' project they were still doing together (Comedy Central's "Key & Peele") is now done, are they even still a "team" anymore?)?
MARK DEMOS I think I heard an interview where they said they were gonna do their own stuff, but try to periodically work with each other in the future.
they're great friends, no competition between them. If peele happened to become more successful (some would argue he is becoming that now) he wouldn't forget key and would probably have him in a bunch of stuff.