IMHO the biggest influence has been the increasing lack of trust in all institutions, but most especially Government, which started around the JFK assassination, and then the Viet Nam war. And now it’s grown to the point that this mistrust is even encouraged and manipulated as a yooge political tool (aka, “it’s all just fake news!”).
Then add the relatively recent phenom of 24/7 “cultivated fear”, enabled & validated by the advent of ‘New Media’ (the interwebs, cable tv, talk radio, etc.)… and little wonder there’s so much rage, mistrust and anxiety, even though we’ve gone thru much worse periods than this, like the Great Depression and WWII.
A common theme of both the gun lobby’s attachment to the Second Amendment and the willingness of ultra-right representatives to push the world economy into a depression in the name of anti-tax ideology, is lack of trust in government. It’s possible to argue that the ultimate source of this sentiment is lack of trust in one another; and there’s disturbing evidence that such a lack of trust — if not contained and reversed — could be a harbinger of a general breakdown in the social order and the consignment of the U.S. to future economic and social backwardness.