Answer: The invasion marked the end of any further negotiation between the superpowers
Explanation: The Soviet invasion of Afghanistan marked the beginning of renewed hostility as the Second Cold War commenced. The invasion led to widespread condemnation of the Soviet union and led the West to believe that the Soviet union was trying to expand.
As a result of this, President Carter withdrew the SALT II Treaty that would slow down the arms race from the Senate, cut off trade contacts between America and the Soviet union thereby blocking various exports including the much needed grain deliveries. The United States also boycotted the Moscow Olympics in 1980, and increased arms spending, proclaiming the Persian Gulf a vital strategic area for American interests and agreed to supply China with military equipment.
The correct answer to this open question is the following.
The importance of the Soviet invasion of Afghanistan in 1979 for relations between the superpowers was that the decision of the Soviet Union to invade Afghanistan represented a hard hit in its relations with Western countries such as the United States. President Jimmy Carter had to deal with this foreign issue in which the Soviet troops landed in Afghanistan to support the Communist government that was fighting many guerrillas that opposed Communism. Those were the Afghan War years, from 1978 to 1992, although the Soviets left Afghanistan in 1989. That tense period was another conflictive moment in the relationship between the USSR that tried to spread Communism and the US that tried to stop it.
