Whilst I 100% agree that something needs to be done about the Japanese-centricity of the Gran Turismo series (a pet topic of mine!!!), I'm not sure that this could be achieved by making each region contribute equally to the overall mix of cars...
Again, I would reiterate that makers of GT need to be a bit better versed in the history of cars and motorsport, in general.
In fact, if the GT series were to truly reflect the "history of the motorcar/motorsport" (or whatever) then I'd say around 65-70% would be based in Europe, 10-15% US and the rest of the world could represent what's left over...
(although I'm willing to concede the US/Europe ratio mentioned above may be inaccurate - I did a rough figure off the top of my head! Suffice to say, though, that Europe/US would, IMO, represent approx. 90% of all motoring activity from the end of 19th Century up until now)...
And before I'm labelled a "whiner" - I have to say that this would be my only *major* critism of GT, as it stands now, and of the direction I think it ought take in the future