The wall won't stop illegal immigration. You under-estimate people's determination. A wall gives the illusion of reinforcement of the borders but it won't do very much to stop it in it's totality.
When my family and I would go camping, we would have to lock out food in containers that prevented the bears from picking up the scent. If we didn't, it was a pretty good chance a bear (or some other animal) would come to our camp site. Guess what... the times we used containers to mask the scent of our food, we didn't get creatures of the night digging through our stuff... Why? We didn't build a wall around our camp site... we just simply didn't give the creatures a REASON to come over.
If the US was serious about deporting illegal immigrants or closing the borders, it could be easily done.
Go after people hiring the illegal immigrants. This comes first because without a job, why would illegals be flowing into the US? They can't find work because no one will hire them for pennies on the dollar. They come here because they know people will hire them to work cheap. People like Trump capitalize and exploit desperate illegal immigrants... why pay an American a fair wage when you can hire an illegal for a fraction of the cost?
Going after people hiring illegal immigrants will have an exponentially greater impact than building a wall. That isn't to say I'm against a wall, I just recognize a wall for what it truly is... an illusion, not a means to an end of illegal immigration.
