From Father Ted to Brass Eye, the Brits have made many funny shows that are totally worth seeking out and not in any way translatable to a mass American audience. After all, Father Ted, a '90s sitcom about a trio of looney Irish priests, wasn't just too silly, absurd, and heavily-accented for US audiences, it was also a show that treated religion with a sense of humor, which is not within the wheelhouse of your average American's comedic sensibility (unless you're making fun of Muslims, which is why Jeff Dunham is a billionaire). Similarly, Brass Eye was a brilliant news satire that makes Colbert look like Red Eye, but it was too edgy even for some UK audiences (its exposé on pedophilia set a record for number of complaints received by the BBC).
While most Americans just think of Brits as pasty, dentally-impaired royal subjects, they've actually done a fine job of mocking the most pompous aspects of their culture since before Monty Python did the infamous sketch "Upperclass Twit Of The Year", and that was over forty years ago. If anything, British humor at its finest is unabashedly silly and ridiculous in a way that many Americans find almost insulting, like the drunk who accuses anyone within earshot of thinking they're better than him. I think it's a fair generalization to say that your average viewer of a Chuck Lorre sitcom would see the Minister of Silly Walks and want to punch him in the face.
So, while The Office is biggest recent sitcom to survive the cross-over, it's one of the rare British comedies to create humor so completely grounded in reality, and even then, by the end of the second season, it had become a completely different show (and already made almost twice as many episodes as the UK original). Still, as the American version made it to nine seasons and the heads of our networks seem allergic to original ideas, we currently have three remakes on or making their way to being on US television; Shameless, Being Human, and Misfits, none of which are all bad, but all fail to come close to achieving the greatness of their Brit originals.
Take Shameless, which is currently on its third season on Showtime, and about to start its 11th (!) and final series in the UK. Like a lot of shows in the UK, Shameless has shorter seasons than in the US, but their seasons started to run longer than most UK dramas (most run six to eight, and by Shameless season eight, they were up to 22—the series will end with an unusual 100+ episodes). That said, despite the shorter seasons and long run, Shameless has had more changes to its cast over its almost-ten years on the air than any American show would. The show is built around the Gallagher family, and while that's stayed intact on the US version, Fiona, the eldest Gallagher, played by Anne-Marie Duff in the UK (and Emmy Rossum in the US), was gone by the end of season two on the original series; as of last season, all of the Gallagher children were long gone.
In fact, turn-over like that isn't uncommon; it's occurred on all of the shows mentioned above, with both Misfits and Being Human now missing all original cast members, and it's usually positive, especially for a show like Shameless that's been trying to stay original for a decade. The American Shameless is already showing signs of strain, trying to create new ways for the same characters to deal outrageously with the same problems; Fiona should just break up with her unreliable boyfriend already instead of having them go through the same cycle of deceit, hurt, and passionately reuniting, a problem the UK show avoided by having that boyfriend be gone by the middle of season two (and he was James McAvoy, not some putz who was in Dragonball Z).
The other translation issue is purely cultural; just as Americans don't like to joke about religion, they also don't like to celebrate characters who cheat, do drugs, abuse the welfare system, let alone on a show that is both silly and strange. While the American Shameless tries to keep all the bad behavior of the original, it has none of the absurdity and whimsy. On the UK show, the musical theme is a goofy, upbeat song with "buh buh buh" for the lyrics, and the score is equally quirky. The show itself is also heavy on dream sequences, voice over, flashbacks, and does feature the occasional musical number. The US version has to take itself way more seriously, using conventional rock songs on the soundtrack and keeping the surrealism to a minimum. Unfortunately, what they fail to realize is, that strangeness is the fun part, not the sex, drugs, and rock'n'roll.
For example, Frank Gallagher, the family patriarch, is a drunk asshole, but what makes him likable isn't the occasional redemptive moment, but that he spends a season carrying a small turtle in his pocket who becomes his best friend. It's also worth noting that David Threlfall, who plays Frank in the UK, is just better at playing the character than William H. Macy is; Macy is a great actor, but he just doesn't sell "narcissist drunken asshole" as well as Threlfall does (pictured in the act above).
While the Being Human remake suffers from some of the same problems that Shameless does, the acting, if anything, is a vast improvement; the show is about a vampire, ghost, and werewolf who are roommates, and while the UK's original werewolf, Russell Tovey, improved over time, he was so bad when the series started, it was like his choice was to portray werewolf-in-human-form as an overly-excited golden retriever. Like Shameless, however, the show is straining a bit by the demand for more episodes with fewer casting changes; Being Human is in its fifth season in the UK, and while their average season is only six episodes, most of its original cast members left at the end of season three.
The remake is dealing with some of that strain this season by changing the dynamic of the characters a bit—the werewolf (Sam Huntington) loses his powers, the ghost (Meaghan Rath) comes back to life, and so far, it hasn't derailed too much from the original tone or dynamic. The characters who have stayed the same, however, are stuck repeating the same patterns over and over again, which makes sense since hey, vampires really are just evil and should be killed (which they did to original vampire Aiden Turner at the end of UK season three, but the US/Canadian vampire, Sam Witwer, just keeps on killin' on, with the occasional sulk thrown in).
Luckily, the show retains the original's sense of humor—it would be a crime to remake a show that's essentially a supernatural Three's Company and try to play it totally straight—but it is a little more tame than the original version, and while it's theoretically set in Boston, its vibe is unmistakably Canadian, which, while not a bad thing, does further mellow things out. Sure, it's nitpicky, but it's hard to for a vampire to come across as truly scary when he says beeen and ouut. It's less Dracula, more Degrassi.
As for Misfits, that remake is still in the works thanks to Josh Shwartz (The OC, Gossip Girl), but I fear for that the most since almost nothing about the original show can cross over intact. The show, which is about five twenty-somethings who get superpowers from a strange storm while doing community service, doesn't just feature the absurd tone and surreal situations that American audiences routinely reject, but unless the show makes it to cable, the equally-unlikable bad behavior will have to get radically cleaned-up, even though it's a big part of what makes the show fun.
Thankfully, all of these shows are on Hulu, Netflix, and/or cable (Being Human has been on BBC America, and Misfits is on Logo for some reason, perhaps because on the characters eventually develops the superpower to change gender?), and between those streaming services, Amazon UK, and, well, bittorrent, there's access, not just to these shows, but I'm Alan Partridge, The IT Crowd, Spaced, Big Train, The Peter Serafinowicz Show, Black Mirror, etc., etc. It's worth seeking them out, if only because they might never make it over here, and might not be as great when they do.