From
http://odur.let.rug.nl/~usa/H/1994/ch10_p7.htm
"The United States, disillusioned by the failure of the crusade for democracy in World War I, announced that in no circumstances could any country involved in the conflict look to it for aid. Neutrality legislation, enacted piecemeal from 1935 to 1937, prohibited trade with or credit to any of the warring nations."
"In early 1941 Congress approved the Lend-Lease Program, which enabled President Roosevelt to transfer arms and equipment to any nation (notably Great Britain, the Soviet Union and China) deemed vital to the defense of the United States. Total Lend-Lease aid by war's end amounted to more than $50,000 million."