I put in all of the G20 powers, and it looked weird that to have France, Germany, and Italy in the middle of the EU, while the EU was weakened quite a bit without them.
I also wanted all of the nuclear powers, bringing in NK, Pakistan, and Israel.
Britain was combined with New Zealand, New Guinea, and the other Commonwealth realms to give Britain more influence.
Venezuela and Cuba were added on account of both being Communist countries in the Americas that dislike the USA.
Iran was added because of how much news there is about it. Afghanistan was included to have a challenge and to help keep Iran in check.
Kazakhstan (et all) was included to help round things out to 31 nations.
ASEAN + Taiwan was included to give the RoC some help. I don't want Taiwan to be doomed to a time of inadequacy.
Caucasia was included simply because that region fascinates me.
Africa was split up the way it was because I didn't want the UN to own almost all of Africa and leave South Africa screwed. I figure basing it on government styles would work, but basing it off of regions could work just as well. I don't think there is a 'right way' of separating Africa in a Present Day Earth scenario.