American foreign policy was shaped by the Great Depression and the WWI experience. An idea that the WWI intervention was a mistake.
The League of Nations failed to make significante changes in Europe
After the WWI, the U.S. was less involved in World Trade.
FDR supported the "good neighboor" policy, reducing the U.S. presence in Latin America.
Between 1935 and 1937, in reaction to the rise of dictators in Europe, and the invasion of China by Japan, Congress passed a series of neutrality acts that banned the sales and transportation of arms to belligerents nations.
The Objectives of the series of neutrality acts was to not to reproduce to mistakes of WWI and limit US involvement as much as possible.
Until October 1937, FDR himself was isolationist. But changed his stance with the “quarantine speech” in which he denounced the “epidemic of world lawlessness” (i.e. dictatorships & invasions)