I've found that there is a strange relationship, or lack of one actually, between the "intelligence" of the individual AIs and the "difficulty" level of the overalol game, even though they are tied together in the game setup screen. Why does the map generator produce a map that is biased towards the AI races farthest from you when on a higher overall difficulty level, but not on a lower level?

As for influence, you can influence any planet owned by any race into a culture flip. I have done it to minor races, and I have even flipped a major race's homeworld, often as the first of their planets to follow me into slav...er...enlightenment.

Yep Pudding's right. TOugh is the hardest non-cheat level. I'm pretty sure the map's aren't biased towards the comp. Luck of the draw perhaps?