What distinguished the United Nations from the League of Nations?

The participation of the United States in the United Nations marked a significant distinction from the League of Nations. The League, established after World War I, lacked the full involvement of the United States, which chose not to join. This absence reduced the League's authority and effectiveness, as it was meant to be a collective security organization but lacked the support of one of the world's most powerful nations.

In contrast, the United Nations was founded after World War II with the goal of promoting international cooperation and preventing future conflicts. The United States was a key player in the formation of the UN and became a permanent member of the Security Council, wielding significant influence within the organization. This participation helped to establish the UN as a more robust and credible entity for promoting peace and security on a global scale, in comparison to the League of Nations.

The other options do not capture the primary distinction effectively. While the UN does address economic issues, that was not a key distinguishing factor from the League. Additionally, while the UN has developed mechanisms for military action, its fundamental differentiation lies in the participation of major world powers, particularly the United States. The establishment of a monetary system is not relevant to the core functions or purpose of either organization.