> I resented being constantly 'corrected' on the local accent I was picking up from school as a child, but now I appreciate that an RP or close to RP accent turns down the difficulty slider in certain British interactions.

The accent bit happens in the US too, to an extent. Depending on the accent you grew up with, you get different responses from people in professional or professional-adjacent settings if you forget to switch the knob back to the more homogenized vaguely Iowa-sounding GenAm accent. This covers a gamut of other accents - regional or not (NE, aave, southern, val, etc).

But it's not nearly as bad as RP in England from what I gather - for one, a pretty decent chunk of the population would normally grow up with a GenAm accent with no forcing, unlike in England where it's a pretty hyper local <5% of the native population.

It really does. The classic example I think of is Michael Caine discussing when he wanted to do housing renovations, and before he even submitted designs, he had neighbours and councillors complaining it was going to be "vulgar," "nouveau," and "obscene" simply because of his class. He also talked about the concept of working class people furthering the divide, for example his female family members referring to women of the correct class as "proper ladies" and putting themselves down.