Except that, even if you don't care for the pantomime style, Doctor Who often rips the shit out of politicians, the military and religion. Plus, there are other British shows like Utopia, Black Mirror, Life on Mars/Ashes To Ashes and Orphan Black (OK - the latter is a US/BBC co-production) that 'do' conspiracies and social comment in ways that the traditional US TV networks wouldn't touch with a bargepole (looking forward to "Humans" although I understand that's a remake of a Scandinavian show). US viewers might not have seen them because they don't have 500 episodes and (with the exception of Who) tend to finish when the material is tapped out.
The US output has got vastly better in the last 20 years, but in the past they really couldn't touch the sort of dark, anti-establishment or morally ambiguous content of British shows like Quatermas, Blake's 7, Doomwatch (X-files without the aliens), UFO, Edge of Darkness (not the film!) or the non-SF 'House of Cards' (original British version). The sets may have wobbled (only UFO had state-of-the-art effects for the time), they all had good and bad episodes, but the stories didn't pull any punches. Yes, Star Trek had a strong social justice message, but it was mostly morally squeaky-clean and moralistic, with nice happy endings.