system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do some cities have a distinguishable accent while others don't?

For example New York and Boston both have a unique accent, but LA has the same accent as Seattle, Chicago, DC etc...
gpt
Well, you can still spot a Chicago accent, or Atlanta or New Orleans...etc.

However the Midwestern accent has been adopted by news, broadcast  and Hollywood., so those are alike by dissemination by the entertainment industry.

Used to be that Hollywood used the artificial, trained "Mid-Atlantic" accent (Hepburn, Gable, Bogart) to appear more sophisticated and blend better into the UK accent, but it was abandoned for the Midwestern accent that the next generation entertainers and newscasters such as Johnny Carson (Nebraska) and Walter Cronkite (Missouri) had.