I don’t know any detailed answer to this.
But I certainly get the impression that some mainstream US movies from 50+ years ago are quite different (in terms of their American patriotism and focus on liberty) than those of today. There’s far less pragmatist ideology in the characters.
Two movies I have recently watched are:
“Mr. Smith Goes to Washington”. 1939. http://www.imdb.com/title/tt0031679/
“The Alamo”. 1960. http://www.imdb.com/title/tt0053580/
IMO, there’s no way these movies would be box office hits today. I doubt characters such as these are even conceivable to people of my generation, they barely are to me and my views on freedom aren’t exactly representative of the majority.
eg/ John Wayne’s republic speech in the Alamo.
eg/ James Stewart’s charater’s moment of personal crises outside the Lincoln memorial.