In Europa Universalis II, nationalism is a special type of revolt risk for recently conquered or diploannexed cities. There are a few exceptions. Cities in core provinces of their owning country do not experience nationalism, and pagan cities do not get most of the effects. colonies and trading posts never experience nationalism. Nationalism also prevents culture change from happening in a colonial city. See the culture article for details. Note that pagan cities won't change culture until their 30 years are up, even though their revolt risk from nationalism is zero.