Why and how did the US help France defeat Germany and what good came to France after the US helped them?
Without the US' help, Operation Overlord (D-Day) would never have happened. Without D-Day, France would have never been liberated. The US wanted to liberate France as the stepping stone to driving into Germany and ending WWII in Europe. Plus the US did feel some kindred towards France since they aided us in our revolution. And the French by and large were very kind to our troops in WWI. I have to set the record straight here to protect ALL soldiers that help liberate France. It was the U.S./Canada/French/Italian who bond together to help liberate. Canada went against Hitler and then 2 years later the U.S. jumped in. All soldiers lost in that terrible war are worth mentioning. Sorry, there were other countries, but the main one was Britain! Remember good old Winston Churchill?
A coalition defeated the German army. England, Canada, US, "Free" French army who fled in England, but also Polish solidiers also settled in England. And many other countries.
What good came after. The US send money with the Marshall Plan and France could rebuild quickly and could know a very whealthy period called "Les trente glorieuses" (The glorious thirty years)