I have not started to watch the second season but I liked the first season a lot. She doesn’t play an American. Her character is an Irish immigrant. So if you watch it you can critique her Irish accent.
Michael Sheen is an actor with a very wide range, from Tony Blair, Brian Clough, Kennneth Williams and David Frost, to Aziraphale and the robot barman in Passengers.
He is one in a long line of excellent comic actors with a wide range, including Alec Guinness, Peter Sellers and Ronnie Barker.
Or as Jake Gyllenhaal put it on SNL, a character actor is an actor whose face you can remember but whose name you cannot.
So did Smoochy 