This is a meaningless statistic. I'm astonished by so-called Christians on Facebook that post homo-promo graphics. When the real persecution comes, the average church will see a 95% falling away. This is what happened in Communist Russia.
“Over 80% in US identify as Christian” is not only a meaningless statistic, it is also untrue. The 2007 survey of religious affiliation and behavior linked below has some interesting results. It shows that many people have shifted their religious affiliation. About 78.4% opted for Christian, although only a little more than 51% were Protestant. Younger people were more likely to be unaffiliated, atheist or agnostic. The immigrant population is providing more Catholics than are leaving that faith. Mormans and Muslims were having the most children. Now to find something more recent.
http://religions.pewforum.org/reports
The link below has many details from many sources from different years with a range of percentages. Under Statistics, a 2012 survey shows 73% Christian. Many references have links to specific sites.
http://en.wikipedia.org/wiki/Religion_in_the_United_States
The link below has several articles regarding trends in religion/nonreligion, especially among the young.
http://commons.trincoll.edu/aris/
To change the subject: I am wondering why it might be considered a bad thing to talk about eliminating the state’s right to allow Liberty University, but consider it a good thing to NOT allow the 650,000 residents of Washington, DC to write their own laws regarding using their own tax money?
And now Russia is 50% self identified Christians. Christianity seemed to have lived on in people's thoughts.