Less likable yet much more extensively featured than Catherine Tate's Valley Girl, Classic Doctor Who companion Peri also falls into The Valley Girl category. Originally from California, her character often falls into the ditzy behavior and emphasis on appearance associated with this trope. Nicola Bryant, the actress behind the role, was actually British and infamous for her terrible American accent made more noticeable than the British slang used in the script.
The Cowboy
https://www.youtube.com/watch?v=cKCw9UKj5QM#t=23m20s
I rarely see cowboys in real life, but they show up all the time as Americans on British television, especially several decades ago. In a 1978 episode of Britain’s long-running comedy Are You Being Served?, Mrs Slocombe’s American uncle from New York comes to her wedding wearing an actual Stetson and reinforces the idiot American stereotype like it's going out of style.
https://www.youtube.com/watch?v=323uSPPJ0MI#t=16s
Other times, The Cowboy trope is less in the aesthetics and more in the attitude. The Classic Who episode “The Tomb of the Cybermen” (1967) features a gaggle of American soldiers, including Captain Hopper, an uncharacteristically competent representation of a Yank. The manly Captain Hopper spends much of the episode off-screen fixing his ship, but still manages to find some time for heroic feats.
This wasn't the first time cowboys made an appearance on Doctor Who. The first U.S.-set episode -- "The Gunfighters" (1966) -- saw The First Doctor hanging with Wyatt Earp and Johnny Ringo. Cowboys were big in early Who, and a go-to representation of an American in British television of yesteryear.
The New Money
The British are known for their period dramas, and none has been more popular in recent years (both domestically and internationally) than Downton Abbey. Unlike many British shows, Downton Abbey has a main character who is American: Cora Crawley (played by American Elizabeth McGovern). Though Lady Cora's Americanness is often counted as a black mark on her character in English society, her family's money allows for her foreign birthplace to be overlooked. This is a common trope when it comes to Americans popping up in British drama: The New Money.
"Don't worry about me, I'm an American. Have gun, will travel!" -- Cora
In British drama, The New Money American is a symbol of change in a dying imperial world. They are usually seen as less culturally refined than their Old Money counterparts, but the manner in which they are treated as characters varies greatly. For Cora, though she is often teased for her more outgoing, casual (read: American) way, she is a resilient, well-developed character who is more than just her Americanness.
The Playboy/Playgirl
Americans on British television tend to be much more promiscuous than the British characters who surround them. Sometimes, it's played as a character flaw, as is the case with Cora's playboy brother Harold (played by American Paul Giamatti) in recent episodes of Downton Abbey. Other times, it's played as part of an American's charm, as is the case with Doctor Who/Torchwood's enigmatic Captain Jack Harkness (played by American/Brit John Barrowman).
Other examples include Peep Show’s Nancy (played by Canadian Rachel Blanchard), who manages to shoehorn the American stereotypes of being uber religious and a New Age hippie with her identity as a sexually adventurous lady.
The Operative
Often American characters appear on British television as operatives. They may not be the main villain, but they are players in the game, if not as members of the actual C.I.A., then as covert corporate players. The American Operative is often threatening, but not always frightening -- more of a nuisance than anything. They are hardly ever the brains behind the operation, but that doesn’t stop them from shows of snarky confidence.
https://www.youtube.com/watch?v=a7R2NhgEeg0#t=3m19s
Jekyll’s Benjamin (Brit Paterson Joseph), a psychopathic employee of Klein & Utterson hired to control Tom (a.k.a. Jekyll) and Hyde, is a particularly effective variety of The American Goon, while the C.I.A. agents in Sherlock’s “A Scandal in Belgravia” prove worse at their jobs.
