Is the Africa bonus just for African countries, or all countries?
North America, Europe, or Asia, not Africa if the Africa bonus is Africa only. If it isn't then Africa is the clear choice, since you can put fighter bases in other locations from what I understand.
Also the South America bonus might not help endgame, but it should push your knowledge forward much faster. iirc the psionics skills need a interrogation of a sectoid before you can start using them, right?