What is post-Christian?

I received an email with a link to statistics about how America is becoming a post-Christian nation?  I know society (and some churches) seem to be moving away from Bible-based principles, nonetheless I found the new term mentally confusing and emotionally conflicting.  So I tried to find a good definition I could share with others who might want to understand the term too.

Merriam-Webster defines post-Christian as "following the decline of Christianity as a majority religion." Wikipedia says it "is the loss of the primacy of the Christian worldview in political affairs, especially ... where Christianity had previously flourished, in favor of alternative worldviews such as secularism and nationalism."  Both are very scary thoughts!

I continued to search for better definitions and found a John o'Sullivan speech where says "It is a society rooted in the history, culture, and practices of Christianity but in which the religious beliefs of Christianity have been either rejected or, worse, forgotten."  He continues into a long dissertation on how this breakdown of morals and manners is:  hurting the family unit, the opposite of freedom of religion, creating false political correctness and over-stepping governmental bureaucracies.

"And it shall come to pass, if thou shalt hearken diligently unto the voice of the Lord

 thy God, to observe and to do all his commandments which I command thee this day,

 that the Lord thy God will set thee on high above all nations of the earth: 

And all these blessings shall come on thee, and overtake thee,

 if thou shalt hearken unto the voice of the Lord thy God." - Deuteronomy 28:1-2

I also found an article by Regis Nicoll who calls post-Christianity "America's Food-Court Faith" because off all the different religions and philosophies within the United States.  The article quotes: a silly articles, other people, and a lot of statistics.  So it is a long read, but it shares hope near the end.

The original study of statistics that started me on this tangent were from BibleGateway.com USA Cities Ranked By Their Most Post-Christian Status.  This was done by actually surveying people.  Just to verify the new data, I searched for religious data on their #1 city and found BestPlaces.net USA/State/Cities had an interesting spread of religion from a city in a state colonized by Protestant Pilgrims and Puritans.  According to their results about 10% are Protestant and 49% are Catholic of the overall 60% with religious affiliations.  Not sure how the city statistics were gathered on the this one as it does not say on that site.  Their chart of USA Religions was interesting even though it also does not say where/how data was gathered.