This youthful exuberance has its benefits but it also has more than its share of idealism, naïveté and general lack of big picture considerations.
The survivalist movement is a great example of this.
This statement simply makes no sense. Americans didn't show up on the shores of New England with their minds wiped clean. American culture stretches back and builds on all of the cultures of the people who came here (or were here already).
It's not any younger than any other places cultures. It may have changed faster because of greater environmental pressure — new physical environment, mixing disparate peoples together — but categorizing it as "adolescent" is simply tribalism. Putting the US down to make yourself feel better about your culture.
Americans have thought similarly about Asia for awhile now, the thought being that Japan, then Singapore, then China, would adopt more American beliefs about free speech and freedom of the press. That hasn't quite happened to this day. I don't think it would ever happen unless the fundamentals change.
An analogy: The snow fox tells the forest fox that red fur is a liability, and you should have white fur like me to stay safe.