Prosperity and adaptive pro-social norms

It is a fact that the shrinking of the American Middle Class is primarily due to the increased prosperity of the nation.  Over the past thirty years, the Middle Class has shrunk while the Upper Middle and the Upper Class have grown dramatically.

I further observe that America has always had a strong communitarian streak, expressed differently in different regions but communitarian none-the-less.  

Which leads to a speculative thought.  The Middle and Lower Class quintiles historically both manifested and benefited from communitarianism.  If your absolute financial condition is either limited or constrained, the value of communitarianism is significant.  All the attributes of communitarianism -  volunteering, donating, community involvement, community engagement, shared values and objectives, civil discourse, negotiation and trade-off decision making, shared community assets (parks, pools, tennis courts, etc.) - are all necessary elements of the culture of communitarianism.  But they are also part of financial necessity.

I wonder whether increasing anxiety and polarization might not be in part caused by the reduction in communitarianism that comes from increasing prosperity.  Not only do people move upwards from one level of finance to another, but the cultural norms and attributes change as well.

It is possible that growing prosperity is not only atomizing society (the more prosperous you are, the more independent you can be) but also driving out some pro-social behaviors like communitarianism.  Is it possible that increasing prosperity and more certain prosperity might lead to greater atomization and reduced pro-social adaptive behaviors?