Final answer:
The United States boycotted the 1980 Summer Olympics in Moscow because of the Soviet Union's invasion of Afghanistan.
Step-by-step explanation:
The United States boycotted the 1980 Summer Olympics in Moscow because the Soviet Union invaded Afghanistan. The invasion was seen as a violation of international law, and the U.S. saw it as an aggressive move by the Soviets. In response, President Jimmy Carter announced the boycott, and the U.S. did not send its athletes to compete in the games.
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