A lot of the funniest people are/were Americans (with a definite emphasis on Jewish Americans). Conan O'Brien, Larry Sanders, Larry David, Carl Reiner, Mel Brooks, Groucho Marx, Woody Allen, Chris Rock, Bill Hicks etc. etc.
I wonder if the American and British sense of humour will elide as America continues to decline as a superpower? Not to suggest that the much vaunted (by us) British sense of humour is entirely dictated by our status as a global superpower, but it's obvious to anybody who spends any time with typical British people that we see ourselves as a sort of nation of (loveable) losers.
The preponderance of funny Jews has to have something to do with the Jews' historical status as pariahs, you'd think.