The parts of the border wall built by President Bush seized property from private citizens. Infamously, there is now a golf course in Texas that is now on the wrong side of the border. So, you have to subject yourself to search by CBP in order to go play golf despite not leaving your country.

Bush tackled the easiest parts of the wall. Expanding will only present more seizing of property from citizens and subjecting citizens to search and seizure solely due to their proximity to the border, despite them having no desire to cross the border. Whether being searched for wanting to play golf is unreasonable is a constitutional issue.