No, it's not Earth, but I have two reasons as to why it'd be situated in South Africa if it were real.
1. As everyone knows, "Equestria" is a town in South Africa
2. The Golden Oaks Library makes sense if you consider SA's Sunland Boabab tree, which is a species of tree that's naturally hollow. No need for magic. It's just a natural thing.
And that's all I've got so far :/