Boy, that's a big subject.
The greatest feature of America was (?) its ability to gather diverse peoples together, to live and worship freely.
Unfortunately, the American establishment of civil tolerance, in the First Amendment, eventually led to civil, and then individual, indifference toward religion and morality.
This transformation may not have been necessary, since Europe, with its established churches, experienced a similar, contemporaneous phenomenon.
This habit of intellectual indifference has spilled over into all aspects of life. It's difficult to imagine how the trend can be reversed. My guess is that only widespread suffering will sober up our society.
Well, that is a given, but it is too broad. This disregards specifically Christian character of worship that marks America, the presence of the Frontier in our mental makeup and I would say the Nordic dominant ethnic character. Today, the "diverse peoples together" has become a liberal mantra and lost its attraction because of that.