Gibb Sahib said:

"One of the few reasons non-USA artists might not achieve this in some cases is..... wait for it.... they sing in a "funny" accent"

Now that statement is interesting because EVERY time I hear/read an American commenting on how we speak over here, they something like,
"We just love your British accent!"
NEVER, " We aren't struck with your funny British accent".

And, getting back to Adele. She is different. People love her personality! Big time! More so - I would say - than any other pop star ever!
For one reason alone, people generally don't even know what the personality is of the majority of pop singers!

I would say that Adele is admired/loved on more levels than any pop singer in history!

I would safely say she resonates with women like NO OTHER female pop star ever!

However, her next album is going to make her the biggest pop star in history or...