Same in Australia. I can’t remember religion playing any part at all in my childhood, and basically every single person i knew was the same. I did go to school with one guy whose parents were religious (probably Anglican, which almost qualifies as atheist in the minds of some evangelicals), and i remember that a downside of staying over at his place for the weekend was being dragged to church on Sunday. Only did it once.
As others have said, it depends on where you live, although i wouldn’t go as far as RitterSport does in suggesting that this is largely a Southern thing. Yes, the South might be considered the major portion of the Bible Belt in the United States, but there are large areas throughout the country where religion is a big deal, and even larger areas where, even if people aren’t openly evangelical, they will still look at you funny if you describe yourself as an atheist.
I know people who come from religious backgrounds, in fairly religious communities, in Virginia, Ohio, Indiana, Alabama, Nevada, Utah, and Washington state. Most of these people are not stereotypical hellfire-and-damnation Christians, but many of them say that atheists and agnostics are considered odd or strange in their hometowns, and that the default assumption is that people in the community will be God-fearing, church-going Christians. Even here in Southern California, home of surfer dude culture and all the wonderful culture and depravity of Los Angeles, there is a very large number of religious people. There are millions of practising Catholics, largely (but by no means exclusively) among the population of Mexican and Central American origin. There are also plenty of conservative Protestants. Drive through Orange County, and you’ll see quite a few massive modern churches on prime real estate, catering to the wealthy Christian conservatives of the area.
I know plenty of Catholics here in San Diego—again, mainly Latino—and in my experience, while they take their religion quite seriously in their own lives, they are not especially concerned to throw it in other people’s faces, and they don’t see another person’s religion (or lack of religion) as any sort of social or moral barrier. A couple of my Mexican immigrant friends from my gym expressed some surprise when they asked me my religion and i said i was an atheist, but it was more the sort of surprise you see if you tell someone you don’t have a smartphone. They didn’t seem to have a problem with it, and it didn’t change the way they treated me.
It also depends, in considerable measure, on the sort of people you hang out with. I teach at a university, and many of my own friends, here and across the country, are academics and other people with advanced degrees. This group tends to be less religious, and far less openly religious, than the American population as a whole. Of all my academic friends, i can think of literally one who goes to church on any regular basis. Her father was an Episcopalian (Anglican) minister, and even she only goes periodically, and is otherwise indistinguishable in her social interactions from the rest of my secular liberal and leftist friends. While it might be difficult, in some small-town environments, to make social connections without the structure and moderating influence of church and religion, in much of the United States, especially in large towns and cities, an atheist will have no trouble at all making a social life.
I grew up in Australia, and i’ve lived for extended periods (i.e., two years or more) in Canada and the UK, before moving to the US, and as an atheist i feel no more constrained or limited in my day-to-day life in America than i did in any of those other countries. It’s certainly true that religion is more central to the big-picture social and political culture of the United States, and i might view the world differently if i were living in small-town Alabama or downstate Illinois, but it really isn’t a big challenge for an atheist to live in America.
When i was in high-school in Australia, that was the case too. A girl from my class went to the United States on an exchange in Grade 11. She spent a year in a town called Lynden, Washington, which is north of Seattle, right near the border with Canada. She came back talking all about the love of Jesus Christ and the need to take him into your heart. Everyone was polite to her, but the general consensus was, “What the fuck?”