So?

Exactly.

I think you mean she sings music inspired by music created in America

Like I said, American-style music.

There are plenty of other threads on singing accent to answer your rhetorical questions, Tunesmith. The conventions are different in every case.

In at least one of those I have stated my observation that some people from the U.K. seem particularly bothered by this concept of a "phoney accent" and/or by the practice of singing in a different pronunciation than one speaks. You'll find this sort of botheration does not adhere in many places in the world.

That leaves it down to an issue of aesthetics within a particular smallish sphere — a certain brand of mainly-U.K. mainly-Folk enthusiasts. It's a valid aesthetic preference, but it's a pretty irrelevant issue outside that sphere.

FWIW, I am in USA and I rarely encounter Adele's music. I think I heard it in the dentist's office last, when I had something done to my teeth in April. When I do hear Adele, I see her as "British."