Why do so many Brits complain about Americans playing Brits?

When there are far more Brits playing Americans these days? I never hear of Americans complaining about Brits like Ewan McGregor, Jude Law, basically the entire cast of Band of Brothers, Bob Hoskins, Hugh Laurie, Gordon Ramsay, Simon Cowell, Jane Leeves, Minnie Driver, Kevin McKidd playing Americans even when some of their accents are rather spotty (McGregor is terrible with an American accent). But does it really matter?