Hmm... I believe the saying goes something like: Link or it didn't happen. Yes, that sounds right.
Even if they were assimilated through diplomacy (you could be thinking of Morrowind), the Argonians rebelled at least once, their guerilla warfare didn't work then(the only circumstances in which guerillas warfare could work).
Some people don't understand that guerilla warfare doesn't work if you don't know the land, i.e, if you aren't fighting in your home. If you don't have at least some support from the people (are Nords going to support Argonians fighting a guerilla war in Skyrim?).
The Imperials never "conquered" Argonia. Tiber Septim himself never ordered his army to march into the interior swamps near Helstrom.
http://www.imperial-library.info/content/pocket-guide-empire-third-edition-war-trees-argonia-and-black-marsh
Now, in the event of a war, the Argonians have at least some propaganda in their favor considering past and current events. (Khahaten Flu suspicion, the conquering of Morrowind...)