This is inspired by Cheaper's thread about the Arizona immigration law. Yes, U.S. Federal immigration policy is a shambles. Yes, we need better enforcement and a bigger gate to let people who just want to work to get in legally. But they will keep coming faster than our society and economy can accommodate them for one reason: Mexico is a failed state. The Mexican government has squandered immense natural wealth, corruption pervades government, business, and law enforcement, and there is an ongoing drug war that has paralyzed the northern half of the country. These factors are driving a wave of refugees across our border--except we call them "undocumented workers" or "illegal immigrants" depending on our political leanings. When a state experiences significant economic and/or societal disruption due to the breakdown of government in a neighboring state, military action is justified.
Soooo.....
Complete the withdrawl from Iraq and leave Afghanistan to the French. Bring our counter-insurgency-trained troops, Predator drones, Apache helicopters, etc. home and annex Mexico. Stop the chaos, clean up the police, wipe out the drug lords with missile strikes a la the Taliban commanders, and make Mexico a place people want to live. Then our immigration problem goes away--permanently. And so does a large part of our drug problem. And consequently our prison overcrowding problem.*
*Don't make the mistake of assuming this is my real-world position. I'm just building a castle in the Sandbox; feel free to add on, knock it down, or whatever. But wouldn't it be great if it were that easy?