Answer:
The failure of the United States to enter a "Golden Age" after Johnson's 1964 victory and the passage of the Civil Rights Act was the Vietnam War.
Explanation:
The war in Vietnam was the longest in American history. It was an experience of failure and frustration for the country, constituting, without a doubt, the most serious failure of the United States in the Cold War.
There was a curious discrepancy in the external environment, where this war was a huge defeat for the country, and the internal environment, where the passage of the Civil Rights Act implied a social progress never seen before in the history of the United States.
