Source: Doctor Who Confidential BBC3
While the watershed is not exactly anything goes, the BBC states that parents should know that after 9pm programming is only suitable for adults. While there is an official "safe harbor" in the USA for "indecent" programming, our current FCC and administration is doing their best to not promote it and scare broadcasters. Any adult's-only window might as well be nonexistant, TV now has to be suitable for everybody 24-7.
Recent news reports say indecency complaints are slowing down in the States, but I maintain this is only because broadcasters aren't pushing the envelope anymore. If things don't get better and the BBC has any intentions of selling Torchwood to the USA, and I'm certainly not saying that should be their priority, they may only be able to sell it to folks like HBO who are currently out of the FCC's reach.
Russell T Davies said he was not allowed to refer to Torchwood as Doctor Who for grownups but lets hope that the show will indeed push the envelope, since good art always does.