The regulation of TV is very different in the US than how it is regulated in the UK. In many ways, US TV regulation is far stricter. For example, swearing and sex scenes tend to not be tolerated on US TV. However, some channels of communication such as HBO and more recently Netflix have found ways of almost completely bypassing conventional regulations.
Unlike in the UK, where watching live TV requires a TV licence, America (like most countries) has free access to what is known as 'basic cable'. These broadcasts are paid exclusively through spot advertising and sponsorship, and are subject to the strictest of censorship regulations, which means that the use of swear words that would be perfectly acceptable in the middle of the day on UK TV are effectively banned. There are some exceptions to this regulation. A 2001 episode of South Park famously managed to get away with using the word 'shit' 162 times in one episode, despite the word usually being considered unacceptable for network television broadcast (even the show's creators were shocked by the decision!).
'Premium cable' channels like HBO and Showtime manage to sidestep regulation by being paid for, and having the channels scrambled, so only paying (and presumably adult) customers can see them. At times, basic cable channels will release 'uncensored' DVDs of their shows with swearing, sex and violence intact. These uncensored versions are often the ones that end up being show on UK television, which is why shows like Mad Men, Breaking Bad and Family Guy have frequent swearing and nudity; the versions we take for granted were certainly not the versions first broadcast on US TV!
Michael O'Malley gives some context to the history of the regulation of Television in the US. He also discusses the importance of the FCC, or Federal Communications Commission, who play a similar role to our own OFCOM.
The FCC's own website gives some information on their mission and even what material they find to be 'obscene, indecent or profane', though exactly what constitutes offending material can be confusing.
True Detective, being shown on the premium cable channel HBO, completely bypasses the FCC's regulations. In the A2 Media exam, it is important to not only note why the dialogue is so gritty and filled with profanity, but also how this relates to audience. Does the violence and sex allow audiences a new way of interacting with TV? Do the producers of the show assume that audiences are educated and worldly enough to negotiate the dark themes? Or is True Detective simply use themes of sex and violence to exploit the audience in to accepting the dominant ideology of the show?