Dave the Gnome,
   I just may have to apologise, somewhat, here!
I’ve spent some time today listening to Robert’s output and he is not too heavy at all on the American accent thing.
   One early performance interested me. When he sings “Babe I’m gonna leave you” he can’t help sounding American because of the “gonnas and the wannas” etc.
That raises a couple of language issues. I remember years ago, Cliff Richard was pulled up by some pop reporter for singing “Do you wanna dance” with the “wanna”, which Cliff wouldn’t usually say, and by pronouncing “dance” in an American way. ( Cliff’s is from the south of England where “dance” is pronounced “darnce”)
   Btw, Cliff defended his use of American pronunciations, saying that it scanned better.
   Interestingly, when Pat Boone, notoriously, covered Fats Domino’s “Ain’t That a Shame”, he, Pat, said he couldn’t sing “ain’t as, being an English major, he considered it bad English. He eventually changed his mind because he thought “ain’t" scanned better than “ isn’t " but I think he was wrong. I think “isn’t” allows more opportunity for shaping the sound.