I was being scammed by Nigerian guy long ago. Later he confessed and apologize from me. Although he didn't return my money. I don't wanna go for this Story. Yeah, Many scammers belongs to Nigeria. But i still don't support mentioning a particular county where you addressed most of people are scammers. Actually scammers doesn't have any particular county. They can originate to any country. It depends whom you faced. Kindly don't blame a whole county due to some bad people.
Where scammers are not there, it is in all countries. If you notice, you will understand how the politicians of your country are scamming money from the people, where as a common man, you cannot find a language to protest. I don't know exactly why you got scammed by a Nigerian. I don't think a country should be declared a scammer by name. You just need to stay away from scammers, don't participate in any project if you know there are scammers.