Are there any American actors who have accurately imitated a British accent?

This might be the right time to bring up the Mid-Atlantic or Transatlantic accent - which I had assumed was just the consequence of someone spending a bit of time on either side of the Atlantic.

Looking it up on Wikipediait appears it was actually a purposeful thing what that you were taught to do to accentuate your class / quality credentials, and was a mainstay of elitist prep schools and the theatre.

Exponents include Frasier Crane, Thurston and Lovey Howell III and Cruella de Ville.

Even before she moved to England I found her speech to be weirdly affected so maybe that’s what you are picking up on.

Let’s not forget Charles Emerson Winchester III.

I’ve found it nearly impossible to tell the difference between John Noble’s English and American posh accent. In real life he sounds very Australian.