What were the top 3 positive effects of World War II on America?

America was a late entry into the war; it remained neutral until 1941. President Franklin D. Roosevelt had adopted a neutral policy that kept the country out of the war. The US did, however, manufacture arms and supply these to the Allied nations. It was only after the attack on Pearl Harbor by the Japanese that America declared war, in December 1941, and entered the conflict on the side of the Allied Forces. America benefited greatly. The three most positive effects were:
1. Economic growth.
America's contribution initially consisted of the manufacture and sale of arms, which meant great profits. Since the Allies were desperate to defeat the Axis powers, they relied heavily on America to supply them with arms and ammunition, a task the country took to with relish. As president Franklin D. Roosevelt stated, America became the "arsenal of democracy." This led to a massive growth in the economy and ended the Great Depression. By mid-1945, the United States had produced 80,000 landing craft, 100,000 tanks and armored cars, 300,000 airplanes, fifteen million guns, and forty-one billion rounds of ammunition.
During and after the war, America became a global economic player. Its contribution led to the end of the war partly because of the manufacture and eventual use of the most powerful weapon the world has ever known: the atom bomb, which was developed in the United States. It used these to devastating effect on the cities of Nagasaki and Hiroshima. This led to Japan's eventual surrender and the destruction of the Axis powers. The war itself came to an end not long after.
2. The war drastically changed perspectives on racial discrimination.
When the US at first assisted the Allies and later joined the war, many African Americans who were desperately poor and unemployed found opportunities in the numerous factories and business which had previously been unwilling to use their skills and labor. Since so many industries had sprung up and large numbers of men later left to fight in the war, there were many positions to fill, and African American men and women were more than willing to work. This led to huge social and economic advantages and introduced an era of positive assertion to a disadvantaged sector of the country. Many African American men also volunteered for service, as did other minority groups. Many laws that segregated people were repealed, such as those in the military, for example.
3. The war became a stimulus for women's rights.
The war had a huge impact on women's lives. Women became economically active since many went to work in the factories and other businesses. The country gained a new perspective on their place in society and asserted their independence. Because so many men had left to fight, women were needed to fill the many vacant positions that arose. Women felt empowered and would further assert their rights after the war ended. There existed a greater liberalism throughout the country, which affected all aspects of their lives. They gained greater economic freedom and even fashion trends were influenced. Women could, for example, wear pants for the first time! They were proud to have played such a significant part in the war effort and were encouraged to fight for greater recognition.
The United States's involvement in the war dramatically changed the country for the good and created a legacy that has left a permanent and significant mark. Though the price was high, much of value was won.