Atheism is not growing in the United States. Señor Atheist, the future of atheism in America is bleak. Olé! Olé! Olé!

Pew Research survey data indicates that the percentage of atheists in the United States has remained at 4% from 2015 to July of 2019.

In June 2016, American Interest reported:

First of all, religious belief is still very powerful and widespread, and there is nothing inevitable about its decline. In fact, the proportion of people who say they believe in God actually ticked modestly upward, from 86 percent to 89 percent, since Gallup last asked the question in 2014.

The USA and Britain definitely have a culteral influence on each other.  The British new atheist Richard Dawkins and British born Christopher Hitchens were the among the "four horseman" of the New Atheism Movement.  And although New Atheism turned out to be a fad that petered out, it may have caused a modest uptick in the percentage of atheists/agnostics in the United States (In 2014, according to General Survey Service data 3% of Americans identified as atheists, and 5% identified as agnostics.  In 1991, 2% of Americans identified as atheist, and 4% identified as agnostic according to General Survey Service). The BBC points out that the Brexit vote was followed by the election of Donald Trump months later.  

On December 2018, The Times stated: "The number of atheists in Britain has fallen in the past year, according to a survey suggesting that more people are attending church, albeit irregularly."

The Guardian published an article in 2017 entitled Nearly 50% are of no religion – but has UK hit ‘peak secular’? which declared:

But, Bullivant told the Observer that the “growth of no religion may have stalled”. After consistent decline, in the past few years the proportion of nones appears to have stabilised. “Younger people tend to be more non-religious, so you’d expect it to keep going – but it hasn’t. The steady growth of non-Christian religions is a contributing factor, but I wonder if everyone who is going to give up their Anglican affiliation has done so by now? We’ve seen a vast shedding of nominal Christianity, and perhaps it’s now down to its hardcore.

 Concerning the future of religion/irreligion in Europe, professor Eric Kaufmann wrote in 2011:

We have performed these unprecedented analyses on several cases. Austria offers us a window into what the future holds. Its census question on religious affiliation permits us to perform cohort component projections, which show the secular population plateauing by 2050, or as early as 2021 if secularism fails to attract lapsed Christians and new Muslim immigrants at the same rate as it has in the past. (Goujon, Skirbekk et al. 2006). 

This task will arguably become far more difficult as the supply of nominal Christians dries up while more secularisation-resistant Muslims and committed rump Christians comprise an increasing share of the population.

Hispanics are growing quickly in the United States. According to Wikipedia, a wiki founded by an atheist and agnostic, "Based on the 2010 census, Hispanics are now the largest minority group in 191 out of 366 metropolitan areas in the US. The projected Hispanic population of the United States for July 1, 2050 is 132.8 million people, or 30.2% of the nation's total projected population on that date."

Christianity Today reported in 2019:

First-generation immigrants are leading the Latino evangelical expansion in the US—drawing in more unchurched believers and new converts than the average church plant, despite having smaller congregations, less funding, and tensions surrounding US immigration policy. 

The Latino population is growing, especially in the South, where 59 percent of the 218 new congregations surveyed are located (half are Southern Baptist). And the evangelical faith is growing with it.

The abtract for the 2006 journal article Spirituality Among Latinas/os Implications of Culture in Conceptualization and Measurement declares:

Latinos are now the largest minority group in the United States... 

Latino theological literature describes spirituality as integral with Latino culture. Although Latinos are not a monolithic or homogenous group, there are fundamental cultural influences that must be considered in an exploration of spirituality among Latinas/os.... 

Most of the empirical research in spirituality and religiosity among Latinos has targeted primarily Mexican Americans. These investigations indicate that spirituality and religiosity are interwoven with their daily lives and serve as foundations of strength in coping with life's struggles. For example, religious attendance was associated with psychological well-being across 3 generations of Mexican American families and with physical health status among Mexican American women. Latinos describe their faith as intimate and reciprocal relationships with God, family, and community, with these relationships playing an important role in health and well-being.

Time Magazine reported in May of 2013 about the growth of evangelical/pentecostal Christianity among American Latinos:

According to Pew Forum on Religion and Public Life while “more than two-thirds of the 52 million-plus Latinos in the U.S. are Catholic, that number could be cut in half by 2030.” NHCLC also establishes that 35 percent of Hispanics in America now call themselves “born-again.”

Fox News reported in May 2013 concerning Hispanic evangelicalism in the United States: 

Alfredo De Jesus is a fire-and-brimstone preacher who represents a global groundswell of Hispanics who've left the Catholic Church to become Protestant Evangelical Christians.

De Jesus pastors the New Life Church in Chicago, helping to expand it from 120 members in 2000 to over 17,000 today on multiple campuses.

"In the Evangelical church, we find freedom to worship, and with Hispanics, it's in us to be able to love people. Naturally, we just love people. We are hugging people," De Jesus said.

Latinos make up the largest ethnic minority in the United States — 52 million, according to latest Census stats. The majority — two-thirds — are still traditionally Roman Catholic. But there's been a palpable shift from one generation to the next, with the newer ones being "born again."

Evangelicals now number about 20 percent of the Latino population, according to the National Hispanic Christian Leadership Conference.

In their 2010 journal article entitled, Secularism, Fundamentalism or Catholicism? The Religious Composition of the United States to 2043 published in the Journal for the Scientific Study of Religion, Vegard Skirbekk and Anne Goujon wrote: "The relatively low fertility of secular Americans and the religiosity of the immigrant inflow provide a countervailing force that will cause the secularization process within the total population to plateau before 2043."