Wow, this would be a rough one with 4 titlists banging around for the last few decades. This is speadsheet-like research one might have to do. Without any numbers to back me up, I might say South Korea, as they were in bed with the WBA for years where even some of there most inept fighters were getting title shots. It seemed like every week a Korean or a Venezuelan (another good pick) was fighting for a title. But again, I don't have numbers to back me up, so its just conjecture.
I don’t know which country....but there are only 2 African boxers in the hall of fame ....that says a lot
my point Mark ...is that an entire continent ...with only 2 hall of famers ... is kinda underperforming
The answer is simple... The USA. By far the most champions, but also far, far more failed challengers than anyone else too.