Initially, I thought that President Trump's call for a border wall could simply be interpreted as a call for greater border security. However, it doesn't really look like that is the case. Sure, he wants more border patrol agents but it is hard to link them to security either because, in terms of apprehensions, the ones we have are not very busy.
Even with apprehensions at low levels, the President wants to increase the number of agents. For several years now, however, the US has had a very difficult time maintaining current staffing levels, let alone increasing them. After winning a $297 million contract, Accenture has been able to fill two of 5,000 border patrol positions
they were hired for. Fortunately, they have only received a few million dollars so far. CBP seems to have already lowered its standards and still can't hire what the president wants.
And then there is the comic that started this post. President Trump wants a wall or fence or something he can call a wall. He might or might not want it to cross the entire 2,000 mile border. However, it's not as simple as building a wall. For the wall to be effective, the US would need to extend roads for the length of the wall. That way agents would be able to patrol the wall in order to apprehend those going over, or under, it. Such an initiative would probably require a great deal more agents than we already have. You would probably need to establish outposts as well, perhaps where agents could stay for a few days. Plus, it's not as if you just build the wall and walk away. The wall and roads would require significant resources each year to maintain.
Much of the border land is owned by US citizens and tribes. Either it'll be very expensive to purchase the land or those who own it have no interest in selling it. Some of the ranchers I've met with outside Nogales moved out to the border area decades ago to get away from the federal government. They are not really interested in more government now.
When reporters looked at this issue around the 2016 election, the company best positioned to provide supplies for the wall would be CEMEX, which probably wouldn't go over too well with President Trump or the Mexican people.
Then there are the environmental costs related to the material used to build and maintain the wall. Migratory patterns would be disrupted and wildlife would suffer. In general, people living along the border don't want additional walls.
I honestly don't get why President Trump wants to make enemies of our neighbors and allies. His misunderstanding of the causes and consequences of migration are really powerful. For me, I would rather
pursue policies that bring the US and region closer together. That, however, will have to wait until another administration takes office in the White House.