It’s not even the classic old saw that Nigeria was a completely artificial entity made by colonialism, blah blah blah.

This is a statement with which I have to vigorously disagree. There really is no getting around the fact that ethnic rivalries between the three largest groups have been the dominant factor in Nigerian public life since the 1940s at the very least; there’s no explaining the refusal on the part of the Northern region to push for independence along with the South in 1957 or Northern reaction to Nzeogwu’s coup and the subsequent Ironsi regime’s attempt to introduce a unitary regime without reference to ethnic tensions. The various peoples living within the country’s borders had never all historically been under the same political authority or even within shared influence of one, and outside the North where Sokoto-led forcible homogenization was well under way, they shared nothing in common by way of religion, culture or even language; Hausa isn’t even a member of the Niger-Congo family tree like almost all other West African languages, but belongs in the Afro-Asiatic group alongside Hebrew, Coptic and Arabic. At least with a place like India there were the Indus Valley civilizations or the Mughal Empire to set the ground for a later sense of national unity, but Nigeria lacked even that much logic to it.

That said, I agree with the rest of your points, and I do think Iraq would have been better off had the Bush administration acknowledged from the start that partition wasn’t necessarily the worst of all possible outcomes. As it is, it will be a miracle if civil war doesn’t break out as soon as American troops begin to pull out, as the Sunnis seem incapable of reconciling themselves to Shiite domination after enjoying five centuries of ascendancy.