Yank here.
"RP" is a new concept to me, although I've studied American English, French, German and Russian all my life.
My concern is that the mellifulous, flowing English we Yanks hear from the citizens of the UK will die.
That is why I watch almost exclusively BBC programs: that sublime, polished, precise English. I'm old school: when I hear Alec Guinness or Laurence Olivier, Maggie Smith, et al, speak, I swoon. Even that mindless Ed(w)ina Monsoon's spoken word was a delight to me back in the 1990s. Let it be Hyacinth Bucket's English and I am repelled-probably because the woman is innately dishonest.
Only God knows what will become of American English. To hear a Southern girl from the deep South speak is nearly like hearing fingernails going down a chalkboard to me. I suppose it's the affectation behind it. I have no idea where the accent and English of my redneck neighbor came from: "phlegm" is pronounced "flame," not "flem." "Can't" comes out "cayyynt." "Fish" inexpliably is "feesh." Horrible sounds to me: I was born in Virginia (the gateway to the south and the USAs oldest imported culture) and spent my formative years in Philly ("beautiful"= "bee-yoo-tee-full" (very quickly) , he was born in NYC, but immeditately shipped to Alabama for his formative years. We're two Yanks, two Southerners, and we sound like we're from different dimensions.
But I routinely get stopped in my tracks by American English. I once drove a Renault 5 to Texas from Virginia-a 3 day adventure for me I still think about. While eating, a charming girl in Texarkana (literally between the two states of Texas and Arkansas) asked me "wan' sum 'kate-chip'? I had no idea she was asking me if I "wanted ketchup," and probably thought me a little dense.
The most amusing Yank English comes from our African American citizens. Their inventiveness with our wonderful (nearly) common language never ceases to amaze. If you speak poorly of someone, you "dis" them. If you're being nosey about someone's busniness, you're "dippin'." Also, the New York City denizens ability to combine profound profanity with common sense and insight and deliver it all within a microsecond of time is something, that, as a Yank, I'm simply proud of. For the people of the UK, it may make the hair stand up on your necks, whatta I kno'?
The English that we don't tolerate is affected English. Can't transliterate it for you, but you'll know it when you hear it-think of yuyppies summering in the Hamptons-that nonsense. Cringeworthy.
This has doubtless has nothing to do with RP, but it was fun to communicate with you, nonetheless. Have a good week.