I feel like there’s a second facet of this. Spoken English in old interviews and movies here in the States often featured an awkward, weird hybrid accent known as “mid-Atlantic“, and it really didn’t die completely out of movies until the 1990s. Until that time, it appears that Americans had some kind of inferiority complex about their regional accents.
Since then news readers in the USA have even adopted a much more genuinely American, specifically Southern California sound, that even began to seep into UK spoken English a bit. (Since about the early 2000s the BBC has started to let newsreaders with regional English accents into the club, which I really enjoy and encourage.)
Since then news readers in the USA have even adopted a much more genuinely American, specifically Southern California sound, that even began to seep into UK spoken English a bit. (Since about the early 2000s the BBC has started to let newsreaders with regional English accents into the club, which I really enjoy and encourage.)