Two sounds in the English language (American) are merging, so in California you will hear the words cot
(something you sleep on) and caught
pronounced exactly the same, whereas in New York, you will hear the two words pronounced differently.
In American English (Eastern seaboard)
cot = the back mid-open vowel (^ or stressed schwa)
caught = the back open vowel
In California, the ^ (stressed schwa) sound is used to pronounce the vowel
in cot and in caught.
In RP British English, the placement would be the same,
but those two vowels would be pronounced with rounded lips.
So, if I wish to fake an RP accent, all I must do is pronounce the mid-back and back vowels with rounded lips, and voila, people will ask me if I am from the UK.
One gal from England even asked where I had lived in England. My husband laughed. I was born in Georgia.
p.s. I do not have the IPA overlay on this keyboard, so I have used the ^ or SCHWA to represent the mid-open back sound.