Why are Jews funny?

I don't understand why saying the word "Jew" is funny.  In South Park, the word Jew is used all the time, without really condescending Jews (although it does that as well).  In Mr and Mrs Smith, Mrs Smith states "I'm Jewish" and the audience laughs.  Other instances of random Jew references include SNL, Simpsons, etc.  Then you have Jews who make Jew references, including Mel Brooks and Woody Allen. 

What is so funny about mentioning Jews? 

It's because the US is made of Christians and non-Christians with a Christian mindset who believe Jews are an outdated and useless version of Christianity with silly hats, as well as East Coasters and Europeans who understand that Jews really like to make money but fail do to having a silly language and accent that no one can take seriously.