In my opinion, decades of corporatist conditioning and manufacturing consent are at least partially responsible for this situation. The corporate mass media has induced distrust in Americans with one another in many ways. One of which is all those articles portraying average Americans as extremely litigious and corrupt with bunk stories on hot McDonald's coffee, etc.

http://boingboing.net/2013/10/21/the-true-story-about-the-wo...

The media focuses much more on crime and how we hurt each other than on the many more cases in which we cooperate and help one another.

In more recent years, corporations and parts of the military-industrial complex have been poisoning Americans against each other via the Internet by astroturfing comment threads, etc. and spreading general fear, uncertainty and doubt with a nice sprinkling of intolerance and hatred.

The mass media glosses over corporate welfare while focusing like a laser on welfare fraud by the poor, etc. They want us to despise each other to gain by the oldest tactic in the book - divide and conquer.

It's been working.