Final answer:
The American people had to live with the constant threat of nuclear attack during the 1990s.
Step-by-step explanation:
The threat that the American people had to live with during the 1990s was the constant threat of nuclear attack. Although the Cold War had come to an end with the collapse of the Soviet Union, nuclear weapons still posed a significant risk. The United States and Russia still possessed a large number of nuclear warheads, and there were concerns about the potential for accidental or intentional use.