Besides the countries already mentioned, France and Philippines are pretty strong. Since around 1990 also countries of the former Soviet Union, like Russia, Ukraine, Kazhakstan, Uzbekhistan. Furthermore, Poland is quite strong. In Africa also Nigeria. Smaller countries, which might be a bit overlooked: - Denmark: Battling Nelson (Danish/American), Mikkel Kessler, Tom Bogs, Johnny Bredahl, Brian Nielsen... - Uganda: John Mugabi, Cornelius Boza Edwards, Ayub Kalule, Kassim Ouma...
Italy deserves mention, as do many of the East European countries who have become relevant in a mere thirty years post their Revolutions.
I think that there were a lot of boxers in Europe and South America, in the pre WWII period, who would have been contenders if they had been based in America. Only the cream of those crops made it into title fights.
