One of the stranger arguments you'll hear from atheists is the argument from geography. "If you'd been born in Iraq, you'd be a Muslim, so how do you know your religion's the right one?"
The first problem with this argument is simply that it commits the genetic fallacy. The genetic fallacy is the fallacy of criticising a belief based on its origins, whether perceived or actual. You'll find that far more than just your religious beliefs are the result of your childhood or culture. In fact, in our culture, we tend to send our children to school to learn anything and everything. Many Westerners mock the fact that, rather than learning about finances, we instead learn "mitochondria is the powerhouse of the cell". For sake of argument, let us assume Iraqi schools do not teach that mitochondria is the powerhouse of the cell. Would the fact that British children learn what Iraqi children do not, in any way, bring this fact into question?
The obvious answer is no. A true fact is never affected by how one comes to know it. Even if you think you've encountered aliens who travelled billions of lightyears just to tell you the Earth is actually a sphere, that doesn't validate flat earthism. Thus, the argument is already fallacious, and therefore invalid.
But a more Biblical response would be "who says I'd be a Muslim if I was born in Iraq?" In the book of Acts, we are told why God has divided us into nations that exist at various times in various places. It is so their people might seek God, and perhaps reach out and find Him. And as it turns out, they do.
As is shown by the fact atheism itself exists alongside Christianity, what you believe is far more than just a product of where you were born. It's what you do with where you were born that matters. Atheists chose atheism. Christians chose Christianity. Muslims chose Islam. It doesn't matter how they came to conclude those beliefs were true, and indeed, every single one of them could come to conclude otherwise. So, the argument from geography doesn't work. If I'd been born in Iraq, I'd still be a Christian, because I'd still be me. It's just that I'd have drawn that conclusion from a different source. Let us pray that atheists, regardless of where they were born, one day realise that the folly of their arguments is a result of the folly of their worldview, then come to Christ also.