Those are games where the Iroquois can conquer the world, or the Viking can become the militant defenders of the Zoroastrian faith.
It's a very big, very complicated scenario that can play out many, many different ways, but it's not the open-ended playground of Crusader Kings or Europa Universalis. The important distinction between Hearts of Iron 4 and the rest of Paradox's strategy lineup is that Hearts of Iron is a scenario, not a sandbox.