Let's start with the Americanised version of Sherlock, starring Johnny lee Miller as Sherlock and Lucy Liu as Watson.
Some people love this idea, with a feminine spin injected into a predominately male series... some want Sherlock and Watson to fall in love. Others... such as me... hate this idea.
I'm not British, but this attempt is similar to changing Harry Potter to an American in a magical boarding school, swapping Mulan to a young Brit during World War I, James Bond to an Indian secret agent, or Aladdin to a Celtic fairytale. Yes it can be done, but why bother?
Sometimes, it can work, but in most cases, only if the series isn't widely known. AMC's "The Killing" based on the Danish Series for one, however Prime Suspect starring Maria Bello didn't make the cut. With the huge success of Walking Dead, Mad Men, Sopranos, Boardwalk Empire, Game of Thrones, and True Blood, original novel adaptations will always rule the airwaves.
I think it's only a matter of time that the smash hit "Downton Abbey" is revised for American audiences. This idea is completely unnecessary, considering the wealth of excellent American writers such as Edith Wharton and Henry James. With the female audience beckoning for more period dramas, (how many more Jane Austen versions can one make?) the time is perfect to launch a series based on three or four sisters in old Boston itching to make their mark on society. After all, history loves ambitious, feuding sisters. Think the Bouvier sisters, the Mitford Sisters, the Cushing Sisters, and now... the Middleton Sisters.
The question is, who will do it first?