I fear you are pretty alone in that opinion - at least, I would hope that most people aren't so worryingly ignorant. As has been pointed out, Mali was one of the major empires of the Middle Ages, not some weird obscure country known only to specialists. I should say it should certainly come higher up the list than the Celts, for heaven's sake, who weren't an empire at all. And I should think it's more mainstream than Khmer. Similarly, Armenia is one of the most ancient cultures currently in existence, not just a "small sormer Soviet Republic". I too would like countries that I "know", but fortunately my historical knowledge, whilst lacking in many ways, isn't so biased towards northwest Europe.