I thought you couldn't really have meant what was implied...
...but I felt obligated to spell it out.
Putting many guns on the border would be an empty gesture unless people began to be killed in large enough numbers to be a deterrent.
When one considers the dangerous conditions that the illegals already endure to get to the US, it would have to be a lot of deaths, and many more woundings. Regardless of their government's competence, we don't need to have that kind of relationship with the Mexican people.
It would also tend to reinforce the opinion of people in this country who think of Latinos as disposable. That's a mental habit we can do without.
Regards--
Mary Anne