Background information: This passage discusses how the United States ratified the charter of the United Nations and became a founding member.What convinced the United States to join the United Nations?

The United States joined because support for the United Nations was broad: both major political parties and much of the public believed the organization could help prevent another world war. The League of Nations had not succeeded in preventing war, so its achievements did not convince Americans. The choice about Wilson and Roosevelt is also incorrect because Wilson died before the United Nations was created.

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