The Neutrality Act had a significant impact on US involvement in World War II. By prohibiting the sale of arms and ammunition to belligerent nations, the act made it more difficult for the United States to provide aid to its allies, particularly Great Britain and France. This made it more difficult for these countries to fight against the Axis powers, and it increased the risk of their defeat.
In addition, the Neutrality Act made it more difficult for the United States to stay out of the war. By allowing the president to sell arms and ammunition to belligerent nations on a "cash-and-carry" basis, the act gave the president the power to choose which side to support in the war. This made it more likely that the United States would eventually enter the war on the side of Great Britain and France.
Ultimately, the Neutrality Act played a significant role in US involvement in World War II. By making it more difficult for the United States to stay out of the war, the act helped to ensure that the United States would eventually enter the war on the side of the Allied Powers.