It doesn’t take long to notice that outside of parts of New York and a handful of 70s movies, people don’t have New York accents.
As tidal waves of yuppies swell into neighborhoods previously reserved for third generation immigrants, it’s a rapidly fading NYC cultural institution. Locally-born kids sometimes try to avoid it to seem worldlier, but new residents try to adopt some flavoring words for authenticity. Tourists seek it, the same way they might look for modern Native Americans to say “How.”. It’s argued whether the different New York accents (yes, there are variations) can be attributed to each of the five boroughs or just class level. Like any regional accent, those who don’t use it often think of it as charming, but ultimately uneducated sounding. (See also Fargo, Valley Girl, Good Will Hunting and Sling Blade.)
Northern California doesn’t seem to have accents. (Am I wrong?) Instead they have some of their own jargon (“hella”, “bounce”, “chillax”, “grass”, etc.). The only exception I’ve noticed so far is with second and third generation Japanese American Californians (Nisei and Sansei, so I’ve learned). I can’t put it into words yet, but you can just vaguely hear an accent that is distinctly not first generation immigrant, but unique. I haven’t heard it with any other second+ generation ethnic group.
More as I understand it.