I can’t find anything there that shows how many Americans as a whole identify as Christians.
ABC 3 years ago: Eighty-three percent of Americans identify themselves as Christians. Most of the rest, 13 percent, have no religion. That leaves just 4 percent as adherents of all non-Christian religions combined — Jews, Muslims, Buddhists and a smattering of individual mentions.
That's quite different from the world at large: Fifty-two percent of the world's population is non-Christian, compared to 4 percent in the United States; and one-third is Christian, compared to 83 percent in the United States. (These are rough comparisons, because the world figures, reported by the Encyclopedia Britannica, are for the full population, while the U.S. figures are among adults only.)
The largest group within the ranks of American Protestants is unaffiliated: Nineteen percent of Americans say they're Protestants, but don't cite a specific denomination. Another 15 percent of Americans identify themselves as Baptists or Southern Baptists,
Thirty-seven percent of all Christians describe themselves as born-again or evangelical; that includes nearly half of all Protestants (47 percent), as well as a small share (14 percent) of Catholics. http://abcnews.go.com/US/story?id=90356&page=1
According to a 2014 study by the Pew Research Center, 70.6% of the adult population identified themselves as Christians, with 46.5% professing attendance at a variety of churches that could be considered Protestant, and 20.8% professing Catholic beliefs. The same study says that other religions (including Judaism, Buddhism, Hinduism, and Islam) collectively make up about 6% of the population.
According to the Association of Statisticians of American Religious Bodies newsletter published March 2017, based on data from 2010, Christians were the largest religious population in all 3,143 counties in the country.[17] Roughly 46.5% of Americans are Protestants, 20.8% are Catholics, 1.6% are Mormons (the name commonly used to refer to members of The Church of Jesus Christ of Latter-day Saints), and 1.7% have affiliations with various other Christian denominations.[2]
A 2015 study estimates some 450,000 Christian believers from a Muslim background in the country, most of them belonging to some form of Protestantism.[22] In 2010 there were approximately 180,000 Arab Americans and about 130,000 Iranian Americans who converted from Islam to Christianity. Dudley Woodbury, a Fulbright scholar of Islam, estimates that 20,000 Muslims convert to Christianity annually in the United States.[23] https://en.wikipedia.org/wiki/Religion_in_the_United_States