No credible stats I have seen places atheists out of single-digit percentages in the US.
The largest self-reported “religious” group in American for a little while now has been the “Nones”, or religiously unaffiliated. This INCLUDES atheists, and so people sometimes conflate it with atheism.
As an atheist, I’m “religiously unaffiliated” for obvious reasons.
But there are also people who believe in the core tenets of Christianity but avoid organized observance. These have varying levels of personal piety, ranging from little to no observance, all the way up to daily prayer and Bible study and perhaps even having services for the (extended?) family in their home, led by the family patriarch. I suppose that all the major religions have people who don’t affiliate with an official congregation yet at least nominally embrace all the dogma except the parts that disparage non-affiliation.
There are those who identify as “spiritual but not religious” in some broader, less-defined sense. They may practice things other than a popular religion, like spiritualism or the Kabala or New-Age types of ideation.
None of this changes that those who are definitionally true Atheists, are a small minority, especially in the US where a third of the populace are evangelicals.
I’m sure we break into double digits in some Western countries, but things are obscured there for different reasons. One is that cultural Christianity is a bigger thing in countries that, for example, once had or perhaps nominally still have a state religion. For example, where the state church is or in cultural memory was the Lutheran Church you might identify as Lutheran in a survey because after all you live in a Lutheran country; you may pay a tax to the church unless you specifically opt out, and probably have a lot of Lutheran influence in your thought habits – even while not personally believing in any God, much less the Christian one, or being in any way observant.