When Isoroku Yamamoto warned that Japan had no chance to win World War II, he famously cited America's industrial might. One of the biggest areas where that strength came into play was with the automotive industry.
As this video by Fiat Chrysler shows, the automakers did step up big when World War II hit. One notable example not covered in the video is that most of the Avengers were not built by Grumman, they were built by General Motors (and thus, they were called TBMs, as opposed to the TBF for the Grumman-built versions). GM also built a lot of Wildcats as the FM and FM-2.
Bofors 40mm anti-aircraft guns. (Screenshot from Fiat Chrysler video)
Chrysler, though, was very good at building tanks. First the M3 Lee (or Grant) was rolling off the assembly lines — in some cases before the factory was completely built! The Grant was eventually replaced by the M4 Sherman. They also built lots of trucks — including the half-ton and three-quarter-ton trucks that were ubiquitous in the military.
This video notes that Chrysler was responsible for about 25 percent of America's tank production — more than all the tank production of Nazi Germany. What is also notable is that many designs that came to Chrysler were improved by its engineers.
Tank treads produced by Chrysler. (Screenshot from Fiat Chrysler video)
Check out the five-minute video from FCA America that explains the U.S. automakers' amazing role in supplying the troops in World War II.