I'm sorry but I just don't think the premise of your question is correct. It's outside of my field of study, so this is a question for someone more qualified (/u/britainopplsnerf or /u/DuxBelisarius) but even with a rudimentary understanding were not France and China both critical?

I can speak most confidently for France but it was the French Army Group, 10(?) divisions, which had at least a quarter million men, which led Operation Dragoon in '44 and '45 which liberated Southern France (Toulon, Lyon especially) while, even more importantly, tying up Patton's flanks and creating a strategic pocket around routing German forces, sending them reeling into the Vosges. The French also had tens of thousands of soldiers fighting under American leadership (notably the French 2nd Armored) until being attached to the Free French Armies in Dragoon et. al. These French forces, of independent command, would notably reach and cross the Rhine and Danube in their French and Italian theater operations respectively.

The only way to say France "contributed very little to win WW2" is to outright ignore their contributions in North Africa, Italy, and especially in their de facto leadership of Operation Dragoon. These things happened. They are simply overlooked because for the duration of the war tens upon tens of thousands of Frenchmen were fighting either under American OOB or were partaking in theaters that are not nearly as notorious in Western mythos. Everyone cares about Operation Overlord and Operation Cobra. No one cares about Operation Dragoon which made the first two possible and liberated half of France.

Can you explain what you mean by saying China was defeated?

You can check what France did in North Africa during WW2 to realize that it was not just a "very little contributon".

For example, the Bir-Hakeim battle allowed English army to prepare El-Alamein battle, and prepare the fight against Afrika Korps. It was 3 700 french men VS 37 000 Germans and Italians.

After the battle, Hitler told during an interview with the journalist Lutz Koch:

You hear, Sirs, which tells Koch. It is well a new proof of the thesis which I always supported, namely that the French are, after us, the best soldiers of all Europe. France will be always in situation, even with its current birth rate, to set up a hundred divisions. It will be necessary for us absolutely, after this war, to tie a coalition able to militarily contain a country able to achieve prowesses on the military level which astonish the world as in Bir Hakeim

A good book on the China part would be Rana Mitter's "Forgotten Ally". It gives a nice overview of the many (maybe lesser known) events that happened in China during World War II. It also tells about the relation between China and the US.

'Very little contribution' is not really argumentative, I think China played a huge part in containing the Japanese Blitzkrieg.