It’s a bit odd, because myself I did believe that Australia should definitely be up here but with the sources I was using I didn’t see it anywhere and it would say they only have 12. I’m not sure where that comes from, but it does. I agree, I could also add those other stuff but I fear people will have issues with that, not knowing if they would know to put that.
You could include former countries, e.g. USSR (473), East Germany (192) – either that or state that only present-day nation states are included.