With America's participation in Vietnam war, military spending grew. It started with Kennedy's little military activity, which later on Johnson would turn into a significant military initiative. In the last period of the 1960's, government failed in raising taxes to pay for this activity, which resulted in the tearing down of the country's prosperity.
The Vietnam War continued to 1975, and after Nixon's resign, America seemed incapable of controlling events, together with economic issues. There was a deficit in trading activity, since cheap imports represented a challenge and inflation rose as well as unemployment. Eventually, America's economic activity decreased significantly, and Vietnam War was the turning point for this.