Here is reality...If we (America's) really did not want anyone to cross the border we could have it come to a near perfect stop any time we chose to. I was stationed near the Czech border before the fall of the Berlin wall. The Russians put up a simple fence with guard towers every hundred yards. Anyone who tried to cross the fence was shot. This was very effective, and also very inhumane. For some reasons we Americans have always needed someone else to blame our woes on. Native Americans, Blacks, Italians, Germans, Japanese, Irish etc etc etc. I really am not sure why this is, but it has been 100% consistent throughout our history. The other thing that has been consistent is all of these groups (and more) have represented a source of cheap labor. We (Americans) have no real desire to close the border because there is too much money at stake. Not in the cost of a wall, fence, etc but because of the loss of a cheap source of labor.
We'll most like pretend to stop the flow of of undocumented persons because for some really strange reason it makes us feel better, but if we were serious you'd see guard towers being put up every hundred yards.
Lets all take a deep breath, recognize that both Mexico and the US are wonderful countries in their own right and enjoy what we have to offer each other. I may be naive, but I have always believed that love, concern, peace and respect wins out in the end. In some mystical kind of way 'nature' has a way to find balance even for us human beings, at times even in spite of our ourselves. God Bless America and Viva la Mexico.