Answer:
The relations between the United States and the Soviet Union cooled during the late 1970s because of the Soviet invasion of Afghanistan.
Explanation:
First of all, the Soviet Invasion of Afghanistan, was originated because the ruling party was influenced by the Soviets. The country was tired of the regime and wanted a change which produced an arousal and was augmented as a religious fight. However in the background was a Geopolitical movement related to strategic positioning, Israel relations and oil interests.
Second, signing of the SALT II treaty was an agreement The US and Soviet Union signed to establish norms and rules for nuclear weapons, but it was never a conflict step stone. Just controversial.
The election of Jimmy Carter didn't influenced the cool down of relations of The US and the Soviet Union. He acted to cool them down but never cooled them down by its election.
The Olympic games in moscow by themselves had no impact on the relations o the relations between the US and Soviet Union, they were inherent.