Between 1974-1999, what problems had a significant impact on the nation and greatly contributed to America being a “restless giant”?
In the aftermath of the Vietnam War, the nation struggled as a giant might to generate positive momentum. There were specific challenges and significant problems that confronted States between 1974 and 1999.
There were many problems or events that led to the US being a "restless giant" during this time period. The ones that had the greatest impact, in my view, are connected to the Middle East.
Perhaps the most important of these was the Iran Hostage Crisis of 1979 and 1980. When Iranians took the American embassy staff hostage, it sent a message that the US was no longer very strong. This embarrassed the United States on the world stage. In addition, there were oil shocks caused by OPEC that did the same thing. They showed how dependent the US economy was on oil from the Middle East and thereby made it harder for the US to "generate positive momentum" that would have resulted in the US looking and feeling like a strong country again.