Why are French people so funny?
This is a pretty subjective question. I will try to provide some observations that may or not apply:

- While being less individualistic than their American counterparts, the French have an impressive capacity for teamwork and cooperation, especially during emergencies such as natural disasters or terrorist attacks. This probably has something to do with more shared history and living in smaller towns/cities where everyone knows each other well.
- More relaxed approach to life can lead to more humor than Americans due to better understanding of "live-and-let live". People also don't take themselves too seriously which allows them to be much funnier overall (as long as you aren't taking yourself TOO seriously :) )
- Despite stereotypes about pretentiousness, it's true that at least in metropolitan areas like Paris or London - most educated young professionals speak excellent English. So when you mix that up against the previous point of culture of sharing rather than ownership this becomes even easier. Also note that unlike other countries' equivalents these professional circles still overlap quite significantly.