Legalizing more immigration will decrease the level of illegal immigration.
But I'm not sure people care about that.
Well, I would assume there's a reason current US immigration laws are as they are, and why they make such entries illegal...
Sometimes, the anti-immigration crowd reminds me of the anti-piracy crowd: they know full well they're not capable of fixing the problem, so they make a show of creating stricter and stricter security measures that fail to inconvenience anyone other than law-abiding citizens.
Well, it's not a binary problem, "solved" or "not solved". It's gradual: What can be done is to prevent as many
people as possible to cross into one's territory illegally.