Except mine. Once again, tell me where any walls are built that have totally failed in their design goal to either keep people by and large in or others out. Right now, all it takes to cross the border are two good feet or a pair of wire snips. How is it that Israel can built a wall that keeps 99% of all but the most extreme, organized and determined out (who eventually get detected and stopped anyway) but the USA can't?
If walls don't work, why is every jail surrounded by one, every secure facility surrounded by one, the Vatican surrounded by one, every castle surrounded by one, every gated community surrounded by one and every Hollywood actor's home who opposes the wall, SURROUNDED BY ONE?
What you need to do is step back and use your head for a moment.
Other countries use walls because they are engaged in wars and / or they want to keep people separated (i.e. as was the case with the Berlin Wall.)
Now, whether you like it or not; agree with it or not the masses of Americans willingly do business with these foreigners. The bulk of the U.S. population has NO interest in keeping people out. You could regulate people coming and going by revisiting the visa system and updating it and modernizing it. You are not going to stop people from south of the border from coming here UNLESS you plan on having the 14th Amendment nullified or voided out.
The wall idea is not going to work when the majority of the American people, if given a vote, would revise the immigration laws rather than build a wall. You said it. You want the wall to keep people out. Most Americans do not want to keep these people out. Consequently, the wall is not a solution. You still have an immigration issue; you still need a solution, but you're only going to trade one set of problems for another.