From what I understand:
Empire: Cyrodiil, High Rock, Skyrim (in civil war), parts of Morrowind (not exactly hospitable as it once was)
Aldmeri Dominion: Alinor (Summerset), Valenwood, Elsewyr, occupied parts of Hammerfell
Independent: Hammerfell, Solstheim, Black Marsh (actually, I am not sure about Argonians)