The United States continued trade during the war without actually entering the war effort because it established the cash-and-carry policy for warring nations.
Cash and carry constituted a policy enacted by US President Franklin Delano Roosevelt at a special session of the United States Congress on September 21, 1939, as a result of the outbreak of war in Europe. It replaced the Neutrality Acts of 1937.
According to the cash-and-carry policy, military arms could be purchased to belligerents on the same cash-and-carry basis.