Doesn't matter what happened generations ago in a war (and knowing roughly the boundaries asserted in those disputes, your explanation doesn't cover nearly enough ground). What matters is the laws to which the land is now subject and, as the settling of the West is complete as those old acts were made to bring about, there isn't one which legitimately authorizes the federal government to continue as owner of most of the real estate in the West. In truth, that broad of a land ownership power probably never existed at all - the constitution is pretty limiting in that realm.
Oh yeah commerce clause whatever. Wrong is still wrong. Here is the means of production of major industries in the western states, claimed by the federal government and enforced through the barrel of a gun. What was that called again?