Final answer:
The League of Nations was important in history as the first international body aimed at preventing war, which faced membership and efficacy challenges, leading to its replacement by the UN after World War II.
Step-by-step explanation:
The League of Nations holds significant historical relevance as it was the first major attempt to create an international organization tasked with maintaining global peace and preventing future conflicts post-World War I. Despite its intention for collective security and dispute resolution, it faced critical challenges such as the absence of the United States, and the inability to prevent aggressive actions by expansionist nations leading up to World War II.
The failures of the League contributed to world history by demonstrating the weaknesses of international organizations without universal support and by laying the foundational principles that would be used to establish the United Nations, a more robust global institution for peacekeeping established after the Second World War.
The League's influence on the United States trended towards isolationism, a result of the Senate's refusal to join due to concerns over national sovereignty and entanglements in European politics. This refusal to ratify the Treaty of Versailles, which founded the League, marked a period where the U.S. pursued a more isolationist foreign policy, avoiding involvement in certain international alliances and disputes.
Ultimately, while the outbreak of World War II less than 20 years after the conclusion of the First World War may be seen as a failure of the League's objectives, it highlighted the necessity for a stronger and more inclusive international framework, leading to the establishment of the United Nations with the support of the United States and initially 51 member states.