Quick Answer: American television networks like to port successful British material because it's proven to have a market with audiences. They tend to Americanize the shows, using the stories and characters in an American setting in hopes that people will better identify with the stories. But the nature of television as a medium is very different in the two countries, and it influences the way stories are told and impacts the essence of the product. Taking a series from one culture and transplanting it to another often results in a loss of the intangible qualities that make the series what it is, and result in failure. Television in the UK is more of an art and less of a business; in America, it's the opposite.
Countless British television shows have been adapted for American audiences. Some become surprise hits, like The Office (2005-2013) or Who Wants to be a Millionaire? (1999-), and Shameless (2011-). Even American Idol (2002-2016) outperformed its UK counterpart by tremendous figures. But the majority of adaptations are flops, simply failing to capture audiences across the pond the way they do in their native country. (Think about Life on Mars, The IT Crowd, Coupling, and Skins, as a few of countless examples. And if you have never heard of those shows, that’s sort of the point.) The primary reason for an American network’s interest in doing their own take on English material is that the shows are popular in Britain, and they want to capitalize on something with a proven history. Yet, most invariably fail when modified for stateside viewing. It all leads to one greater question -- why bother? British shows are already English-speaking programs, and adaptations are usually done while the original series is still fresh and current in society. So what’s the point? And why don't they work?
There are actually a number of reasons why American television can’t keep its hands off British material. Humorously, most of them are the same reasons why the shows often don't succeed. A bit of it is cultural, while the rest is economic and deals with the vast differences in the business of television in both countries.
The American cast of The Office and the UK cast of The Office
George Bernard Shaw once said America and Britain are “two nations divided by a common language.” With the various dialects and accents and ways of speaking in the UK, many Americans have a hard time following English-speak despite it being the same language. There are cultural differences and turns of phrase and manners of speaking which permeate English television and which American audiences often fail to appreciate, which diminishes the quality of the show.
That’s why Broadchurch (2013-) came to America as Gracepoint (2014), and David Tennant traded in his thick Scottish accent for a dreary American one. That’s why the wonderful Olivia Colman was replaced with the tall, blonde, very-American Anna Gunn. That’s why the Latimer family's surname was replaced with the California-correct Solano family, and the series was relocated to America’s favorite state. American producers like stories better when they are about Americans. And then, keeping with the example of Gracepoint, the series failed because in its translation to the American format, it lost the charm and personality of the original. For lack of a better word, it lost its Britishness, and turned into another thin, heartless, over-produced FOX drama series which found its plug pulled after one season, like countless other FOX programs. It made the mistake of crafting the pilot episode as a shot-for-shot remake of the Broadchurch pilot, which after failing to convert itself to the culture of its new audience, came across as more of a poor Broadchurch cosplay than a compelling drama with depth. Gracepoint's flat story about cops investigating a death is something American television has ad nauseam, and is why the series is so lauded in comparison to its European source. The difference between Broadchurch and, say, The Office, is in the awareness of that transition and the subsequent sense of authenticity. The latter quickly modified itself to the culture of the American public while holding onto the construction of the show. It became unique against the landscape of other available sitcoms. Also consider the wildly popular Coupling (2000-2004), Steven Moffat's sitcom often cited as the British version of Friends (1994-2004), failed miserably in the USA -- nothing was done to make it culturally relevant. Plus, we already had the actual Friends, and it was still on the air at the time.
Of course, many American people don’t have access to British television. Without a cable package that includes the likes of BBC America or without a Netflix subscription, many of these shows simply would never make it into American homes. Meanwhile, everyone is capable of watching FOX or NBC, free of charge. This fact tells networks that even if an adaptation pales in comparison to the original, most people won't know. Thus, in an effort to get the job done quickly, they tend to remake the series as-is and hope something sticks with its new viewership.
All of the above points fingers toward the real reason for these adaptations, and their frequent failures -- format. Television is a product of its origin, and each country, each cultural market, has its own take on how television should be made. American and British television shows look different, feel different, and perhaps most importantly, are made under very different systems of production. Taking a series and transplanting it into another television system and another culture of audience sounds easy, but it's not.
American television is all about money. It is produced by major studios with tremendous budgets and can afford to do everything big, every time. British shows, by comparison, are still typically produced with what one might consider shoestring budgets, at least in comparison to American series. UK seasons are shorter, the budgets are tighter, and they are typically required to produce quality content in a more pressurized environment. This results in a completely different approach to creativity and storytelling. This is why Americans who watch native English television enjoy doing so -- the programs inherently feel different. They are an opportunity to witness the art of a different culture in its native form, not cribbed on FOX in a manner that has been skewed by foreign translation. That’s why Broadchurch and Gracepoint can have the same shot-for-shot pilot episode yet feel entirely different.
There is often an “if it isn’t broke, don’t fix it” mentality in porting British television to America, but given the circumstances, that’s really an illogical approach.
Both casts of The IT Crowd, which never took off in the states
Television in the US and the UK simply don’t operate the same way. The unique manner in which each exists colors the material and gives it its cultural spark. Expatriating a show from its country of origin and thrusting it into another stifles that spark, and for most series, snuffs out that which makes it what it is.
British television is still predominantly public. Everyone pays licensing fees for television in Britain. Because of that, British TV is largely funded through public money, not advertising. Obviously, this is the exact opposite of how television works in America. It’s a for-profit business. In the UK, every network is in competition with The BBC. They compete by focusing on quality, not on commercializing. This is why British television seasons are shorter, with 6-8 episodes per season, as opposed to the American 18-24. British networks aren’t padding airtime with commercials and advertising runs the way American TV has to, so there is no need to fluff out the content. The result is more succinct plots; stories don’t need stretched out as much to make room for constant commercials, resulting in shorter runs. That’s also why there are often years between seasons of shows on British television. It’s not an urgency to get a series back on the air on a specific timeline to begin collecting advertising money again; if there is no new material to present, they don’t present any, because quality comes first. When there is more story to tell, they make more episodes. If you’ve ever studied a British actor’s IMDB page, you’ve probably seen them on 15 different television shows for a handful of episodes each. That isn’t because these shows aren’t good or have all been failures, it’s just the nature of the business. And it's so different from what we do here, not everything can make the jump.
On an American program, producers typically know they have a good amount of time to build various story arcs and slow down character development because they have all those episodes. In the UK, with half to a third the amount of episodes, it all gets done in a much tighter timeline. Neither system is better than the other, it’s just the way they are done, but it’s also a primary business/economic reason why porting a British show to America is a challenging prospect. Turning a shorter-run series into a longer-run American show requires a change in the nucleus of that series’ structure, and that modification can warp everything else. How do you take a series that normally runs a few episodes per season and start stretching it to 22? Usually not well.
The UK cast of Coupling, and the American cast (canceled after 4 episodes)
American networks should realize that British material can work well stateside. Doctor Who (1963-1989, 2005-) and Downton Abbey (2010-2016) are surely arguments to that point. But simply licensing an original British show and airing it on an American network doesn't have nearly the revenue potential of redoing the entire thing, even with the expense of producing another series from the ground-up. If it's a hit, the studio owns it, and the money flows.
Of course, none of this is going to stop the practice of redoing shows from other countries. There are simply too many great series around the world, and American networks can afford to try their hand at success and lose a dozen times for every win. Television history isn't without its successes, and every network is looking for another The Office or American Idol to justify all the flops in-between.