The Pasuk writes that Avraham dwelt in the land of Cana'an, while Lot dwelt in the cities of the Plains... Does this mean that they were not part of Cana'an?
Ramban: What the Pasuk means is that whereas Avraham chose to live in any part of Eretz Cana'an, Lot opted to live in the area of the Plains exclusively (even though it too, was part of Cana'an).
Seforno: Even though S'dom was part of Cana'an, the inhabitants of Sedom at that time were not Cana'anim (but rather even more wicked than they). Consequently, Avraham chose to live with the Cana'anim, who were not nearly as perverted as the Sodomites. 1
QUESTIONS ON RASHI
Rashi writes: "[Lot] pitched his tents until S'dom' - for his shepherds and flocks." How do we know that the tents were for them?
Gur Aryeh: The verse has already told us that Lot himself lived in the cities (presumably with his family).