WW2 raised a generation of poor young farmers out of that life and into one where they went and liberated a country they probably didn’t know anything about.

They didn’t know/care that France actually has a pretty impressive military track record.

So, they come home telling everyone that the French sure don’t know how to put up much of a fight, are helped to become successful in life (unless they were black), and their dumb kids all assume they can kick France’s ass, because they’re weak.