If you are going to build a large wall that spans across a large distance then you should make the wall profitable.
I would cover the top half of the wall in solar panels and place small holes in the wall to channel wind into turbines, such a project would harvest free energy.
Perhaps it could be named the great wall of America and be used for tourism. Perhaps projectors could project TV and image advertisements on the wall.
Or the wall could back up into flats so the back wall of a flat is the border wall. Perhaps many buildings could be built against the wall so one side of the wall doubles as part of a factory or warehouse to save on building materials
The wall itself could be hollow and act as a giant linear city creating jobs for millions of people.
A railway line and road could be placed on the top of the wall to move goods from the Pacific ocean to the Atlantic. like a type of panama canal.
