The wall idea in 2016 sounds too far fetched and ridiculous, the amount of work and resources to build it and then maintain would be too much to afford. It actually makes it look like a clown, I wonder if he could've kinda implement a new technology to keep the border safe, drones, night sensors, etc, even if it bullshit and never work at least the public would be interested on it.
True, no matter how tall you build a wall people find a way to get over it. Take the great wall for example. It's massive project expanding decades to finish. It works then because no one could fly over it, they don't have siege towers or machines that could decimate it then. They don't even have the firepower to actually destroy that wall but people actually found a way to get over it. Today, unless it's a sophisticated enough wall, you'll not completely eliminate the chance of people getting over that wall, at best you just lessen it.