The war efforts brought the return of prosperity, and in the postwar period the United States consolidated its position as the world's richest country.
This is becasue the war itself brought works to million of America as industrial production also skyrocketed to meet the demand of the war. The spending of government on the economy also served to stimulate economic growth.This was necessitated by the facts that the USA participation in the war was not as long as the allies, and the USA economy and infrastructure was also not hit by the war.