By doing this all you are making trouble for your own people. Who knows that PayPal does not share fraud and fake data to fraud checking website like Maxmind. In Maxmind, Nigeria, etc is marked as highest fraudulent country so whoever place order they are blocked on most of site and need to manually verify their details. Double check by some website. They are facing this issue because of some fools who use fake data, details.
The issue with non-supported country is mainly driven by fraud data. If one country has high fraud rate, then Paypal most likely to decline the transactions. For example Nigeria, it is not only in Maxmind, but also in FraudLabs Pro high risk country. It is more data, so if the fraud rate dropped in the future, it should be removed.