Population (in millions)

NA/EU:
EU 508
US 316
Mexico 117
Canada 33
Aus&NZ 28

Total: 1002M (just over 1 billion people)
# of servers: 25
Pop per server (in millions): 40

Japan 126M
# of servers: 25
Pop per server (in millions) 5

This results in a 8:1 player to server ratio for NA/EU vs Japan

These are raw #s and don't reflect the % of the base population that play MMORPGs.
Japan may have a higher % of base population that plays compared to US/EU zone.
I'm pretty sure the %s of players to base population in the US/EU zone is pretty constant across US/UK/CAN/AUS/NZ. Mexico may be less.
Feeling generous we take that into account and reduce the ratio to 7:1

For Square Enix to provide the same level of gaming experience for the rest of the world outside of Japan, they would need to provision approximately 175 more servers.
These capacity numbers are not a requirement that appeared overnight and should have been identified very early in the design stage.