1. Isolationists advocated non-involvement in European and Asian conflicts and non-entanglement in international politics. Although the United States took measures to avoid political and military conflicts across the oceans, it continued to expand economically and protect its interests in Latin America.
3. Lend-Lease and Military Aid to the Allies in the Early Years of World War II. During World War II, the United States began to provide significant military supplies and other assistance to the Allies in September 1940, even though the United States did not enter the war until December 1941
I was confused by chosing between two first options but then I've realized which should be the right one. The only one option that suits to be the major cause of the post-war recession in the United States is the third: 3. transition from wartime production to peacetime production
This Influenza (flu) Pandemic killed between 20 and 100 million people (estimates differ) - more than the war itself! The source of the Pandemic is still not known, and people suggest such places as the US, China and France.
The completion of the Transcontinental Railroad greatly affected companies that made products in that it made it far easier for them to transport their goods over long distances to markets, which greatly increased profits and output.
