Well that's people "you know" - even in Belgium according to these statistics, people who identify as atheists or nonreligious are only 31% of the population, so even there they are still a minority statistically, though a fairly large one compared to the US.
https://en.wikipedia.org/wiki/Religion_in_Belgium
Plus if your argument is, in a broader sense, that being religious or spiritual is contingent only on "church attendance" or directly mentioning "god", then I see problems with that.
Since that wouldn't account for a "spiritual but nonreligious" category who don't openly attend a church. Or religious which don't directly mention a "god", such as forms of Buddhism.
So I think unless someone can come up with a consistent definition that distinguishes "atheist" from religious or spiritual to begin with then the arguments are flawed.