I forget the actor who said it, but they pointed out that drama is more accepted in English schools. Not "Hollywood" or "movies", but stagecraft, and because we're more exposed to American media, we can ape your accents more easily. The result being that we have more ability to *PERFORM ON STAGE* and *USE ACCENTS*! So, our actors seem more well-rounded that Americans, who tend not to be encouraged to engage in the dramatic arts, outside of a few schools on either coast.