Well, the thing about US is that the range of accents is VERY narrow compared to the UK. It's reckoned that there is a greater range of accents in a small area of Yorkshire than the WHOLE of the USA.
Now, I can't quite believe that, but that's what the lanuage experts say.
So, whatever American accent Bruce has, it's a lot, lot closer to his "New Jersey" accent than any Brit singing "American".

And, that's another reason why Brits should sing in their own regional accent because they are so diverse and rich. And, surely the American's should find that interesting.

Why? Because those Yanks, so I've heard, just love the way we talk.

And, don't start telling me that rock/blues sung in UK/Irish accents wouldn't work because that's nonsense!