If we don't need it....then it will not matter. Just look at it as infastructure spending. And some will be direct spending in your state of AZ. Good for your economy.
While the idea of stopping illegal immigration and/or illegal drug flow is something most americans want, building a wall isn't the answer. A lock on your door won't stop a burglar from entering your house. It may discourage them (maybe they'll go to another house that isn't locked), but if they want in, they're going to get in. The same is true of a border (any border). If someone wants to get across a border, a wall won't stop them - no matter how massive one builds it. They'll simply go under, over or around it.
In a nation struggling with economic class structure, spending billions on a wall isn't good use of taxpayers money. As those in the category known as 'middle class' get squeezed out of existence, the number of "poor" will increase (more so than than the upper-class). As the number of poor increases, so does the government's expenditures to take care of them. To get this money (and money for other "necessities" in running a government) one must raise taxes. They may not use the word "tax", but whether its called a fee, a toll or whatever, it's still something citizens must pay. The upper class sure don't want to pay for it (many of them either run or are members of the government). That just leaves the poor. Even now the "poor" are struggling just to survive. Homelessness is rampant across the nation - and is growing. Families are forced to work 2-3 jobs in order to survive. Those jobs aren't perk-laden, full-time, high paying jobs either (education has become too expensive for the poor), they're part time, minimum wage jobs. One can't live off minimum wage! Forget buying a house, these people can barely afford rent - and even that keeps rising. Corporations love find ways to make more money by charging more for less (product sizes are smaller, they raise or add fees to your utility bills to pay for damages caused by their years of neglect and incompetence, airlines charge you a fee for everything (what's next, a breathing fee?)). Upper management make billions while their employees are forced to live in cardboard boxes and practically starve. (incidentally, while you were reading this, the rent on a cardboard box rose 25%).
So now they want to build a wall. Who's going to pay the billions needed to build this frivolous wall? Taxpayers. How? Higher taxes. Who pays these higher taxes? The poor (the rich get their taxes lowered). But the poor have no money to pay as they're already massively in debt. So they ask the government (the rich?) to help them. The reply? "If you have time to complain to us you must not be working enough. Rise the taxes higher!"
A wall not only keeps things out, but it also keeps things in - things like animosity and discontentment. Pharaoh wants a wall, but is refusing to give the slaves straw forwith to make the bricks. History has shown time and time again that when the poor are so downtrodden that they have nothing left to lose, revolution is close at hand.