Out of all the super hero movies that have come out of hollywood the past 20 years....a HUGE percent of those lead actors are non Americans.
Best Actor Oscar is supposed to be the epitome of US acting profession.
5 out of the last 10 winners were NON Americans.
From the action film angle, and the dramatic lead angle.....international actors are making their mark in Hollywood.
The full story goes beyond the roles that Black Brits have landed recently.
I suspect it's a matter of quality plus quantity. There are a ton of British actors with extensive and varied acting backgrounds. On top of that, they generally command less per film because....while their actors are good, they seem to produce fewer mega stars given the number of good actors.
I also think there's a "blank slate" factor. Top shelf American actors are easily recognizable. Lesser known but talented British actors can give you a similar level of performance but "become" the character more easily since we (American consumers) don't recognize the Brit as easily. We might be like "ah, that's ol dude from that show" but that's about it.
It's been going on for years. I mean freaking Stringer Bell and Jimmy McNulty are as English as tea and crumpets.