These were very different eras for the US.
Right after WWII, the US was booming at home and was facing the beginning of the Cold War with the Soviet Union. The US economy was growing rapidly as people started to be able to buy things again after the war. In foreign affairs, there was a great deal of worry about the Soviet Union.
By the 1970s, the US economy was slumping. This was the decade of "stagflation." In foreign policy, this was the era of detente. The US (which was not feeling very strong in the aftermath of Vietnam) opened relations with China and reduced tensions with the Soviet Union.
In these ways, these were very different times for the US.