This is from earlier this month. The opening line of the article reads:
The share of Americans who identify as white and Christian has dropped below 50 percent, a transformation fueled by immigration and by growing numbers of people who reject organized religion altogether, according to a new survey released Wednesday.
Not to say that Christians are the minority. They're still at around 70%. Just white Christians are no longer above 50%. For various reasons, including rises in Christianity from other races while white members are falling away.