I know people say it shouldn't be built - but I don't understand why people say we "can't" build it when they've been built before, and we've done endlessly more complex things - rockets, going to the moon, et (all while China is building artificial islands and the like).
In comparison to some of those feats, a wall seems trivial.
Let’s consider some of these details. Something I think people don’t consider is that there are a non-trivial number of land animal species that migrate across the border. They have no concept of nation-states, and for some, our xenophobic electorate is basically passing a death sentence. The wall would devastate several important ecosystems, especially in the Rio Grande Valley.
Walls also need to be maintained, like any other piece of infrastructure. Have you ever visited the great state of Michigan? We can’t even handle roads. How will the federal government, which doesn’t have the best track record with maintaining infrastructure, deal with a 2,000+ mile-long wall?
Another issue is surveillance. Who will watch the entire thing? Who will make sure someone isn’t chipping away at the other side with a spoon or trying to dig under it? You can’t watch thousands of miles of wall very easily.
There are all kinds of issues with this (oh, funding is a big one too), and this just scratches the surface. If you Google “Trump border wall problems”, plenty of articles have already been written that go into much more detail.
Roads have different material and structural requirements than walls. Maintenance will obviously cost money, but it serves a purpose. 450,000 people were caught in 2016 trying to illegally cross the southern border. Now imagine how many made it through. I assume you will not find this argument very convincing if you are the kind of person that believes that illegal immigrants make money for the state they illegally live in.
CBP border agents monitor the wall. And again, it isn't just 2000 miles of wall. It is "smart wall", where it will have the most impact to prevent crossings
The wall is so people can't just mosey across the border. Even if you had cameras there, sending out a team once you see someone crossing would be very difficult to find them. With the wall, it will be passable but will take work and a fair amount of material like ladders, ropes, etc which will all take time, and allow for security to arrive with a greater chance of catching people.
Assume you need 3 people to drive out to apprehend illegal crossings for officer safety. You also then need 3 others to watch while others are out apprehending and then be able to respond for other illegal crossings.
Assume 3 minutes to cross over the barriers per person.
Assume it takes you no time to see the crossing happen, you can tell the second a ladder is put up.
Assume the roads are dirt, but in good and dry conditions. So you can travel about 40 mph on them on average, including the time to accelerate from 0mph at the remote watch tower station and then back down to 0 to apprehend people. 40mph is 2/3 miles per minute, btw.
So, the minimum distance at 3 minutes to cross would then be 2 miles. Meaning you'd need about 6 guys every 2 miles. So about 12,000 people for the 2,000 mile border.
Now you can play with the numbers, and talk about capturing people that scatter into the interior, but you're still at about 1 officer per 1 mile (ish), not 1 officer per 10 miles or 100 miles of border, with significant downtime per officer per day.
Yeah there's no way any friendly, rational person can look at Mexico and possibly come to the conclusion of "no thanks, I'd prefer not to have that here".
Mexico has no problem with extreme prejudice towards the rest of Latin America. Policies that people would decry x1000 if the US did them to poor Mexicans. But somehow the US applying some basic restriction to Mexico is "xenophobic" among other horrible phobias.
[0] https://en.wikipedia.org/wiki/Thalweg [1] https://cardsagainsthumanitystopsthewall.com
FWIW, i did indeed mean to imply that Trump's wall is absurd and will never be built. I assume that, like the Channel bridge, the Hyperloop, the Freedom Ship, etc, it could be built, given enough time and money. I just don't think that there are enough people who think it's worth the cost to pay for it.