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.
It would be the "Midway Atoll" that is is south of the Hawaiian Islands in the Pacific Ocean, and this was the location of one of the most pivotal battles between the US and Japan in World War II.