British accents and BBC attitudes

I've been a subscriber to Netflix for almost as many years as its existence. However, I am not finding as many new Hollywood releases with the appeal of previous years.  Instead, I have enjoyed a host of foreign films, British comedies and dramas, and lately some British action series - among them several seasons of MI-5 -the British equivalent of our CIA.

The MI-5 portrayal of the CIA is amusingly lopsided.  Gum-chewing top-level administrators, agents with jarring fake American accents, and almost always a mole or traitor in their midst.

It's the accents I have the most issue with (or should I write "with which I have the most issue"?)
Seems that when some British actors try to create a genu-ine American accent it will sound nasal, stilted and stiff.  Just can't overcome the high-falutin' English upper class tongue.  Not to mention some of the dialogue written for the Americans!  Do our lovers nowadays call each other "honey"?

Some British actors can create a standard American accent without flaw - witness Matthew Rhys in the series "Brothers and Sisters" or Australian Rachel Griffiths in the same series.

Note: in the interest of accuracy - the reference to "American" in this post refers to so-called standard non-regional English spoken in the United States.  This used to be the only speech permitted on radio and television - nothing with even a tinge of southern, accented, slangy.