> Dividing the world into "Pagan countries" and "Christian countries" is both inaccurate

That's not what the post said. Just that, before Islam was even a thing, those countries that Jews lived in which these days are considered "Muslim countries" were broadly "pagan" and/or "christian", depending on time and location.

As for your assertion of no christian countries thousands of years ago, where you state yourself "Armenia converting about 1715-ish years ago": That's thousands of years (as in: more than 1000)