I don't know if I was born 50 years too late, but I believe that the WWII era and shortly thereafter was the US peak.
In my mind, much of the decline has been due to some of the things that occurred in the 2 decades after. The, "life is rosy and the US is grand," period of the 50's that was rightly earned by the vets and America in general seemed to be rebelled against by their baby boomer children. You can often see this show through in the Hollywood (hollyweird) movies that are set in the 50's. In these movies, the people are depicted as naïve, goody-goody, and plain stupid; hardly the same people who struggled through 4 years of war less than a decade previously.
Those men desired and deserved the good life and it disgusts me that many of their children find that desire despicable. That desire was somewhat expressed in the movie, "To Hell and Back," where one character says, "After the war, I'm going to have about 6 kids and when they big enough, I'm going to line them up and tell them what it was like here, in Italy. If they don't cry, I'll beat them."
Many people these days are complacent. They desire a quick fix to every problem, both real and imagined. The "fixer" is too often seen as the government in one form or another using "free" funds. They don't realize that those "free" funds are in fact their own, taken in the form of taxes and a small portion returned as a generous hand out.
Citizens don't realize that with every right they enjoy, they also must fulfill one or more responsibility. A responsibility to cast an educated vote goes along with the right to vote. As the accompanying responsibilities are ignored or neglected, rights will begin to disappear. Rights will probably continue to disappear until the citizens, once again, begin to appreciate the meaning of freedom.