Final answer:
The League of Nations was weakened by American refusal to join.
Step-by-step explanation:
The statement that is true about the League of Nations is that it was weakened by American refusal to join. The League of Nations was an international organization established after World War I with the goal of preventing future conflicts. However, the United States, led by President Woodrow Wilson, did not join the League of Nations. This weakened the organization and limited its effectiveness in maintaining world peace.
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