Courtesy USA NetworkIrish actor Jason O’Mara plays an American doctor in USA’s “Complicaitons.”

BEVERLY HILLS, Calif. — Ever wonder why so many European actors are starring as Americans on television? They speak with such flawless Yankee accents that most of us don’t realize they’re beating us at our own game.

Dominic West (“The Affair”), Jamie Bamber (“Battlestar Gallactica”), Frances O’Connor (“Mr. Selfridge”), Martin Freeman (“Fargo”) are all English. Robert Taylor, who plays the rugged Wyoming sheriff on “Longmire,” is really Australian, as are Anna Torv (“Fringe”), Melissa George (“The Slap”) and Simon Baker (“The Mentalist”).

Few of us knew that Diane Kruger, the American cop on “The Bridge,” is actually German and that Rebecca Ferguson from “The White Queen” is a Swede.

It all began with “Band of Brothers,” says casting director Cami Patton. “When we did ‘Band of Brothers,’ we were shooting in England, and we were trying to match actual people. We had a lot of biographical material. We had the pictures of the real people. We had interviews with them (when they were) older. We were trying to do a service to their natural accent and come as close to them as we could. And we had to find the majority of the actors in Europe,” she says.

“(British actor) Damian Lewis had been in New York doing ‘Hamlet’ with Ralph Fiennes, and that’s how he got on our radar. We weren’t specifically looking for a lead. We really actually went into it thinking the ‘core’ guys would be Americans and everybody else could come from anywhere — as long as they could do the accent. We’d seen everybody, and he blew them all out of the water.”

From that point on, she says, it was a natural progression. “You have access to casting directors all over the world, to agencies all over the world. People’s ease with — and with being able to self-tape with equipment that is decent enough that we can actually see what they’re doing and what they look like. All of that has sort of evolved in the last 10 years to where it’s just gotten easier and easier, with every given production to be able to find those people from everywhere.”

This technology has flooded the talent pool with players worldwide. “And producers and show runners and networks and studios are much more used to now looking at tape from other countries. People self-tape. They’re more open to someone coming from somewhere else,” Patton says.

“They don’t need it to be someone necessarily that they know the entire history of. They’re excited when we’re able to introduce someone to an audience as new, who’s 40 years old, who has all of the confidence and experience to pull off the lead in a show, but just is not known to our audience. It’s not that we set out to do that, but it’s exciting to us.”

Though they’re often unsung heroes, casting directors can help make or break a show. Miscasting a lead can be deadlier than a hollow-point bullet. How many TV shows have littered history because the wrong person was cast?

The opposite is also true. Some casting is simply magical. Could anyone but Kelsey Grammer play Frasier? Is there any other actor who could match John Goodman as Roseanne’s tubby hubby? Could Walter White break bad by anyone but Bryan Cranston?

It’s only recently that the importance of the casting director has been recognized.

“When it first started it was secretaries who were casting,” Patton says. “And so for a long, long time, the idea was — for years and years — it was not the most respected job. People didn’t set out to be casting directors. They became casting directors because whatever it was they were trying to do didn’t work out, either acting or directing or whatever.

“And it took until probably 20 years ago for people to start actually realizing it’s a career, and it’s a good career, and what the demands are and what the job qualifications are in order to be able to do it.”

So what do they look for when they’re casting their nets? “It depends what the role is we’re looking for,” says casting agent Wendy O’Brien. “Like with ‘Sons of Anarchy,’ we have sort of a mandate of we don’t want, in general, familiar faces. We don’t want to distract you from the world that you’re watching,” she says.

“If somebody happens to be just a well-known actor, I mean, if they’re really right for the role, if they’re going to elevate the role, or if they’re unknown, it’s whoever is going to bring the role to the most interesting dimension for the viewer to watch,” she says.

Rachel Tenner, who is casting director on “Fargo,” says, “I think on something like ‘Fargo,’ when it’s a one-season situation … we have access to getting bigger names because they know they’re only committing to one year and then they’re done.”