Every wall has two sides. It can't do one unless it can do the other. Only honest folks in control of it can keep it from being used to keep us in if we want to go. In your experience of government, how likely is that to be perfect and permanent?

In mine, it's neither right now.

Edit: also, why do we even need a wall at all? What's keeping Border Patrol from doing it's job, as it has more or less for decades before?

Politics, and nothing else. How will a wall make our politicians better? If they're just as corrupt after a wall is up as they are now, they're going to get the invaders through it, over it, and around it anyway, because that's what corrupt politicians are paid to do.

This influx of immigrants is a result of corrupt politics, not the incompetence of the Border Patrol or lack of a wall. Prior to 1965 and the change in immigration policy, we didn't have this problem. It's deliberate, created by politicians, and going to keep happening with a wall too, because politicians can make a wall as porous as air.

The problem is politics, not construction.