From the Pew Research Center:
The religious landscape of the United States continues to change at a rapid clip. In Pew Research Center telephone surveys conducted in 2018 and 2019, 65% of American adults describe themselves as Christians when asked about their religion, down 12 percentage points over the past decade. Meanwhile, the religiously unaffiliated share of the population, consisting of people who describe their religious identity as atheist, agnostic or “nothing in particular,” now stands at 26%, up from 17% in 2009.
Both Protestantism and Catholicism are experiencing losses of population share. Currently, 43% of U.S. adults identify with Protestantism, down from 51% in 2009. And one-in-five adults (20%) are Catholic, down from 23% in 2009. Meanwhile, all subsets of the religiously unaffiliated population – a group also known as religious “nones” – have seen their numbers swell.