Most people who live at the border or are familiar with the border know that a Berlin-like wall stretching from San Diego to Brownsville is not necessary. And the costs would be prohibitive. And there are places on the border, such as the Arizona desert or the open terrain around the Big Bend in South Texas, where Mother Nature has created her own barrier that is not easily passable. Or if you do pass through it, you are easily detected.

America should be working more with the Mexicans to prevent the flow of guns going south into Mexico that have fueled so much of the violence there, and the smuggling of cash and the money laundering that transnational criminal organizations have instituted in North America, including in the United States.

Every air traveler entering Mexico is vetted against US databases. The air passenger screening system Mexico has in place involves these checks against US national security and criminal data bases. There are plainclothes US officers stationed at airports in Mexico working with Mexican immigration officials to protect the United States. This joint security program has been in place for at least six years and is a huge asset.

People should remember that Mexican migration is now at a net negative. More Mexicans are leaving through deportation and voluntary return than are entering the United States legally and illegally.

We can't defend the country by looking at the borderline as the first line of defense rather than as the last line of defense. We have to secure the flow of goods and people by engaging with foreign entities. We assure our security by securing the flows as early as we can before they arrive and as far away from our borders as we can.

In today's digital online world, those who don't share information will be isolated and left behind.

The image and the costs of a Berlin-like wall or a Great Wall of China is something that the American people have not accepted to date.