Indeed and I think many colleagues will share similar experience. Of course, this is not a matter of being racially insensitive or prejudiced again a country/region, its just pure statistics.
In the line of work I've viewed far too many fraudsters from Vietnam for example. Nigerians and South Africans are not far behind and Indonesia+Russia complete my Top5.
Still, I'm strongly against forbidding a certain country access of service, due to the high-risk state (except embargoed countries ofc). Most verification checkers like MaxMind do take this in mind, but this is just to serve as a flag that a certain customer might need special monitoring. Once a detailed verification is made, contacting the customer is very useful. You can ask simple questions like "What do you plan to do with your website?" or "Do you have any specific email requirements?" - you would be surprised at how many frauds fall easily in this trap, either unintentionally, or just because they don't know better
If needed - ask for an ID verification, if the person is truthful they will understand and even approve of the further security checks, as a sign that the host is taking solid measurements about customer protection.
Give much trust to your clients...but not too much or risk becoming the class dummy