I think the game needs a way of shrinking the influence zone. Lets say people in America have lots of Churches, Librarys, and good universities( which they do). After a while people in Canada may want to live there. Now lets say some other country burns our librarys, and universities to the ground, and outlaws religion. Will the Canadains still want to live here? I think not! In fact I think Americans would want o live In Canada.
The same should apply to Civ3. Bombing temples, Cathedrals, Librarys, and Universities should shrink the cultural sphere of influnce.
Culture points in Civ3 are cumulative; if you destroy the culture buildings, they will, of course, stop to build further culture, but the points already produced, will remain.
I also wish there would be a culture penalty, but for atrocities like nuking, razing cities, pillaging and starving cities without need.