[bee_rider]

Some British accents have implied a sort of eliteness in the US for much more than a couple decades. See the transatlantic accent. By the late 19’th century it a widespread enough sentiment that we made up an accent to copy it.

https://en.m.wikipedia.org/wiki/Mid-Atlantic_accent

[eternalban]

Americans used to have an inferiority complex vis-a-vis Europe (in general) and English. WWII put an end to that. People the world over started aping Americans, including the English. It is (strangely) after US decides to officially be ‘an empire’ that our propaganda organs started speaking posh language. (No one :) affects a cockney accent, ey?)