Answer: Right away, I must admit that no question about World War 2 irritates me as much as this question. The reason is that the right wing, and most notably, Rush Limbaugh, has criticized the "poor" performance of the French as a way to punish them for not going along with former President George W. Bush's fiasco in Iraq.
I am also incensed because I live in Louisiana where at least a third of the population is of French heritage, and yet, I have had to watch these Louisiana descendants of France attack their French cousins as if the French were a mortal enemy of the U.S. They even talked of renaming the French Quarter of New Orleans to get rid of the "French" word. It hurts me to see people deny their heritage and it really hurts to see how fellow Louisiana citizens are naive enough to listen to the likes of Rush Limbaugh.
But to return to the question. There is no doubt that the French fought poorly in World War 2. But they were not cowards. Time and time again, the French prepared to face frontal onslaughts by the German forces only to find thmselves outflanked and outsmarted and were forced to retreat, again. The Germans under brilliant generals like Guderian and Rommel, were too smart to make frontal assaults unless it was absolutely necessary. They preferred to attack weak points rather than strong points.
The old French generals, experienced only in World War 1 trench warfare tactics, never knew what hit them.
No, the French were not cowardly - they simply got the crap beat out of them by a much smarter military force. The French were prepared for a World War 1 trench warfare-type fight. They were unprepared for the German Blitzkrieg assault which featured mobility and quickness.
The French lost badly but they were not cowardly. They were just stupid. There is a difference. See France in World War 2 for more on the French defeat in World War 2.