Defeatism masquerading as realism.
It hasn't been tried. All prior deportation initiatives - the early 20's, early 30's, and the fabulous Operation Wetback in '54 - were stunning successes.
And I have no idea where you live, but having spent the first 18 years of my life 60 miles north of the border back when they routinely deported any illegals, I can tell you there was not a word of Spanish to be heard for decades, even there on the border.
And the narcotraficantes and illegales of Mexico were terrified of U.S. law enforcement, which they should be.
But the current contempt for U.S. law is the result of the consummation of the '60s attitude of ignoring inconvenient laws, aided and abetted by arrogant judges. The criminals of Mexico (that would be most of the government, and virtually all of its businessmen) figured this out and the resulting chaos and invasion is what came of it.
But these guys are punks - and they respect force. I guarantee you, if the U.S. moves against them in a hard way, they won't fight back - they'll realize that we aren't a bunch of cowards.
And in Mexico, if you don't do that, they will think that of you.
And then you're cooked.
So don't talk like a squeamish little coward and make excuses for why we shouldn't act. We have a right to and they know it. When we do so, they'll realize they're dealing with men again, and not a bunch of little boys.