Well, they built enough to manage to destroy some ancient saguro cacti… which is supposed to be illegal… and to desecrate Native American lands and burial sites .
Trump had a celebration about having built 400 miles of new border wall… though not surprisingly, that wasn’t very true :
”Using data from a regular CBP status update, we conclude that, of those 371 miles:
* 16 were built where no fencing existed before;
* about 170 were built where only “vehicle barrier” (structures that could block a vehicle but not someone on foot) existed before;
* about 135 were built to replace older, shorter fencing; and
* 50 miles are new or replacement “secondary wall” built parallel to existing fencing.
As that status update indicates, this has been built—and continues to be built—at a cost of approximately $15 billion in 2017–2020 funds. (Our best current estimate is $15.067 billion.) 70 percent of that money was not approved by the U.S. Congress, as our constitution dictates.”
(That last link goes on to describe several other considerations about various types of damage and harm caused by the wall project.)