Well, based on the information from The Infernal City, the Argonians actually abandoned everything they had taken during the invasion. The novel implies they did so willingly, though the information in Dragonborn indicates that House Redoran managed to mount a counter attack. In all likely hood, it is a combination of factors, but the end result is that the borders haven't really changed.
In fact, with the exception of the Dominion, the borders of Tamriel haven't seemed to change much at all. The only alteration to a map i can think of would be renaming Vivec City to the Scalding Bay.