War weariness: The First World War had a devastating impact on Europe, causing widespread destruction and loss of life. The American public was war-weary and eager to avoid future conflicts. They wanted to focus on domestic issues and economic recovery rather than getting involved in international affairs.
Disillusionment with the League of Nations: The United States played a leading role in establishing the League of Nations, an international organization aimed at promoting peace and preventing future wars. However, the Senate refused to ratify the Treaty of Versailles, which established the League, fearing that it would entangle the United States in foreign conflicts. This rejection contributed to isolationist sentiment.
Rise of nationalism: After the war, a wave of nationalism swept across the United States. Americans were proud of their country's role in the war and wanted to focus on their own national interests rather than on the problems of other countries. This inward-looking perspective reinforced isolationist tendencies.
Economic nationalism: Many Americans believed that the United States should protect its own economic interests rather than become involved in foreign entanglements. They were concerned about competition from European economies and wanted to focus on developing the domestic economy. This economic nationalism further contributed to isolationism.
Congressional power: Isolationist sentiment was strong in Congress during the period between the world wars. Many lawmakers were opposed to international cooperation and resisted efforts to promote American involvement in international affairs. This resistance bolstered isolationist policies.
As a result of these factors, the United States pursued an isolationist foreign policy during the interwar period, choosing to remain largely disengaged from European affairs and other international conflicts.