Look, we all know this isn't factual. But it IS funny.
The French really did save us back in the Revolution. We didn't have a professional officer corps, and Washington, who ought to know, thought that the various foreign officers like Pulaski and Lafayette truly pulled our fat out of the fire and we'd have been lost without them. Apparently if you look into the founding of West Point you find that a lot of people (Jefferson among them) were violently opposed at first to creating a "military caste," but Washington was convinced we needed professional officers and cited the foreign examples as proof.
And they did fight well in WWI, but it wasn't a grand victories kind of war. It was a war in which defensive theories predominated so it ground to a halt. The introduction of fresh troops in large numbers from America tipped the scales, but it's dangerous to think we saved the French because we were so superior to them.
WWII. . . . well, look, I think it's like this. France built the Maginot Line, upon which the Germans would have smashed themselves to bits in the last war. It turned out not to be the solution for the next war, because suddenly the Germans were ever so mobile and able simply to go around the wall. That's easy to criticize now, but at the time. . . . how many times have we done the same thing? We all think fondly of the Garand as the old reliable warhorse, but our own Marine Corps refused to adopt it until they were in the thick of WWII. They were fighting the last war. Nobody would call the British losers at warfare, but they were ordering massed charges and cavalry movements against entrenched machine guns in WWI. Lee sent Longstreet's men on an attack that made them march uphill in the open in full view of artillery for a mile before the attack at Gettysburg! We've all done it.
Everyone makes fun of the French for surrendering so quickly. Are the Poles cowards too, then? The French lost because they weren't ready for the tactics of mechanized, high-speed warfare with lots of movement. The nature of the tactics dictated that the matter would be decided very quickly if Germany was successful, and they were. Were we ready? Would we have fared better? If the German mechanized divisions had started from, say, Niagara falls, would they have taken Washington in a matter of weeks? Might not have taken that long, with the shape we were in. But we had the opportunity to get our collective act together before we jumped into Europe against the Nazis. They didn't. I can't help but think that it was a good thing the Japanese didn't have the wherewithal to do something like that.