Part of the problem is that there is an extended cost to hosting servers in a different country, and it includes time and resources to deploy patches and updates to hardware. For Australia, it was a matter of finding a hosting service, and that actually took a long time. Hopefully servers for Latin America, hosted there, can be a reality one day, but it will require a user base to show to Blizzard that the investment would be worth it, for the long run.
Hopefully they will never be a reality because blizzard will shunt all the people from northern states and Canada unto those servers to help support their queue times.