Why did the industrial output of the United States during the war astound the rest of
the world?

The automobile industry was uniquely suited to the mass production on military equipment. They began to produce trucks, jeeps & tanks. They also produced artillery, rifles, mines, helmets…etc. Henry Ford launched one of the most ambitious projects when he offered to create an assembly line for the enormous B-24 bomber.

Explanation:

roosevelt believed that in light of the country's recent military successes, it was unnecessary to use force to achieve foreign policy goals, so long as the military could threaten force. this belief, and his strategy of “speaking softly and carrying a big stick,” shaped much of roosevelt's foreign policy.