The believed the U.S. should follow the policy of isolationism.
The Great Depression and the memory of World War I contributed to the anti-war feelings in the USA. Isolationists advocated non-involvement in European and Asian conflicts. Congress refused the membership in the League of Nations because it did not want America to get involved in any military conflicts again.
Neutrality Acts were passed which were intended to prevent the U.S. from supporting either side in a war. Tensions were growing in Europe and Asia but the American were not prepared to risk their lives and livelihoods for peace abroad.
The overall neglect for military involvement resulted in the appeasement policy in the early stages of World War II.