A single bullet through the head of an intruder would send the message to all that the border is enforced.
Illegal immigration would come to an immediate halt.
We, as a nation, are much too sophisticated for a simple solution, even one that has been proven to work in many nations. Try sneaking into Mexico, for instance, and see how you like it.
Simply put, a person in the U.S. illegally is an outlaw, that is one who is outside the law. Citizens have rights, illegal aliens have none. NONE! They are outside the law. Put a bounty on them, problem solved. Unfortunately, too simple for our over-educated, can't-change-a-tire ruling class.
There was a movie a couple years back that had an ice age hit the US so American refugees streamed into Mexico and “welcome arms”. I think I laughed out loud in the theatre because the Mexicans would probably machine gun down a hoard of US citizens if they descended upon them.