She’s now lived back in London for nearly 8 years. Her partner is English and her two youngest kids are English (being that they were born and raised here). Her accent is not ‘fake’, people.

That guy from House is completely believable as an American.

Hugh Laurie? Are you kidding me? He may be believable, but it’s nothing to do with his ridiculous accent. You’re right about Yvonne Strahowski, though. I haven’t seen enough of Damien Lewis to judge, and I’ve never even heard of Sarah Shahi.

But these are all lower tier, TV actors, not zillion dollar movie actors.

There are it seems a plethora of British actors mainly not well known actors, who can pass for Yanks.

That’s mainly because Americans as a group are not terribly sensitive about accents, so they tend to give foreign actors a pass with their attempts at an American accent as long as the sound ‘natural’, i.e. consistent and comfortable. British audiences (and American Anglophiles), on the other hand, will only consider an American actor’s attempt at a British accent passable if it’s virtually perfect.

Gillian Anderson, who a previous commenter said had a horrible British accent actually spent most of her formative years in England.

I’ve lived all but the first six years of my life in England, and I still can’t do an English accent. Gillian Anderson’s English accent is OK, but it sounds affected.

Not to be too technical, but there is no American accent unless the American is speaking a foreign language. Dialects are determined by the region where you live. English speakers have a number of dialects, so they usually have the ability to mimic other regional dialects and sound realistic to most English speakers. On the other hand, they usually can’t fool natives of a particular region. They really have to emerse themselves in that region to fool natives.

If you speak a foreign language, it’s almost impossible not to have the accent marks of your native tongue. Even when speakers haven’t spoken the old language in years, they still have accents in their adopted language. That’s why you’ll rarely find a German speaker do a realistic English accent from any region – not unless that German speaker was raised in a bilingual environment.