The problem is that the Constitution doesn't allow the federal government to own any land. It specifically says, "To exercise exclusive Legislation in all Cases whatsoever, over such District (not exceeding ten Miles square) as may, byCession of particular States, and the Acceptance of Congress, become the Seat of the Government of the United States, and to exercise like Authority over all Places purchased by the Consent of the Legislature of the State in which the Same shall be, for the Erection of Forts, Magazines, Arsenals, dock-Yards, and other needful Buildings. . ."
Nothing at all in there about making the Louisiana Purchase, or owning 70% of a state's land mass, etc., etc. It's very clear that the Feds don't need the vast majority of Alaska to erect forts, magazines, arsenals, dock-yards and other buildings.