Question

How did the United States support the Allies with economic aid while staying out of the fighting during WWII?

Answer 1

Hint: World War II, with the conquering of Poland by Germany and ensuing declarations of war on Germany by the United Kingdom and France on the 3rd, is generally considered to have started on 1 September 1939.

Complete answer:
In September 1940, during World War II, the United States began supplying the Allies with substantial military equipment and other support, even though the United States did not join the war until December 1941. Via an ambitious scheme known as Lend-Lease, much of this assistance poured into the United Kingdom and other nations still at war with Germany and Japan. In fact, the United Kingdom urgently needed aid, as it was short of hard currency to pay for the U.S. military supplies, fuel, and raw materials it needed.
The 1939 Neutrality Act authorized belligerents, but only on a "cash and carry" basis, to buy war materials from the United States. The Johnson Act of 1934, which included Great Britain, also restricted the expansion of credit to countries that had not repaid U.S. loans made to them after World War I. The American military resisted the diversion to the United Kingdom of military equipment. General George C. Marshall, expected that after the dissolution of France, Britain would surrender, and so American supplies sent to the British would fall into German hands.
Initially, British Prime Minister Winston Churchill had requested that Roosevelt provide the destroyers as a gift, but the President knew that such an agreement would be opposed by the American public and Congress. British Prime Minister Winston Churchill had initially requested that Roosevelt provide the destroyers as a gift, but the President knew that the American public and Congress would oppose such an agreement. The United States entered into loan-lease agreements with more than 30 countries over the course of the war, delivering some $50$ billion in assistance. Lend-Lease represented a vital U.S. contribution to the fight against Nazi Germany at a time when most Americans opposed direct participation in the war.

Note: The involvement of America in World War II had a significant impact on the United States' economy and workforce. American factories were retooled to produce goods to support the war effort, and the unemployment rate fell to around $10$ percent almost overnight.