Hypothesis 1: It only seems that way. Due to survivorship bias, American audiences are only exposed to the best British humor. Possible test: see if British audiences rate American humor higher than British humor. (I anticipate the answer being no, though.)
Hypothesis 2: The process that cultivates American comedic talent is flawed compared to the process that cultivates British comedic talent. I think the process that cultivates American comedic talent is comedy clubs. Possibly these excessively encourage pandering to the lowest common denominator. I have no idea what the process that cultivates British comedic talent is. Possible test: look at comedians who were cultivated in one country but attempted to find success in the other. (I anticipate sample size being an issue.)
Hypothesis 3: Due to cultural differences, Americans find British people saying funny things to be funnier than American people saying funny things. May be hard to distinguish from Hypothesis 1, as it may also be true the other way around. Possible test: find something humorous that has been performed by both British and American comedians. (I can't think of anything like this off the top of my head.)
Hypothesis 4: It only seems that way to you. Due to cultural differences, British humor appeals more to high-IQ people and American humor appeals more to low-IQ people, and you are generalizing excessively from a small sample of you and people you know. May be related to Hypothesis 2. Possible test: ask people on the street whether they think American or British comedians / shows are funnier. (May be many confounding variables.)
I suspect that British culture in general tends to value a sharp sense of humor more highly than American culture. Bill Bryson, a writer who's lived about half of his life in each, wrote that in his experience a British man would likely be less offended by being told he was a terrible lover than that he had no sense of humor, whereas in America he found a sense of humor to be treated as more of an optional extra.
This is the monthly thread for posting media of various types that you've found that you enjoy. I find that exposure to LW ideas makes me less likely to enjoy some entertainment media that is otherwise quite popular, and finding media recommended by LWers is a good way to mitigate this. Post what you're reading, listening to, watching, and your opinion of it. Post recommendations to blogs. Post whatever media you feel like discussing! To see previous recommendations, check out the older threads.
Rules: