I think some of the crapping on the french comes from a cultural tradition, since America is culturally British in a lot of ways, little though we like to admit it, and one of those ways is a sort of cultural pasttime of hating the French.

Some of it is due to behavior that happened during the intervening +/- 200 years since the Revolutionary War, like America forgiving French debts in the middle of a major crisis, only for Americans to be spat on and swindled in the streets of Paris. Not to mention the open contempt a lot of French seem to have for Americans.

And to be honest, the French make it almost as easy as New Jersey to make fun of them sometimes...