Scammers are everywhere and trying to say they are all from Nigeria could be a wrong saying. I know it s looks like the country has so many scammers that are duping people from all around the globe. I don't mostly base on word on sentiments but I most observe well.
It is not much about scammers from all around the world purposely trying to steal money and at the same time trying to tarnish the global image people have on Nigeria. It is mostly about how Nigeria is viewed from a perspective of popular culture, part of that popular culture is the recurrent scam of the Nigerian prince we all know about.
In general, from my own experience and research on internet, organized scams are from both African countries and South Asia, while hacking and spear fishing comes from eastern Europe and Russia.
On the matter of popular culture and the view on Nigeria and others countries like India, there are several YouTube Channels of people from the west who try to fool and distrupt the operations of scammers in several ways, since those videos have millions of views, people learn those scammers have a very thick accent when trying to talk in English and are from India/Africa. It is an unfortunate reality.