In our faith there is a difference between venial sins and Mortal sins. Not helping a God's souls in need is much closer to mortal sin, than breaking "Ceasar's law" to try and feed your family.
Yes, there should be reform. As you know, in the Catholic tradition, migrants occupy a position of almost unique reverence. They evoke our biblical heritage and have built our Church. They serve as the Church’s metaphor for itself and for the human condition; we’re a pilgrim people in a pilgrim church, passing through the world on a spiritual journey to our final home. They allow the Church to realize its mission on earth of gathering into one God’s scattered children. They provide the means for our conversion and a measure by which our lives will be judged. They are our “brothers and sisters” and, in them, we see our God: “I was a stranger and you welcomed me.”(Matthew 25:35).
To simply consider all "strangers" enemies is NOT Christian in my faith. Those that are enemies should leave, those that haven't committed mortal sins should recieve compassion.
I know I didn't say that. Who did? I think you have just tossed out what is commonly called a straw man.
At any rate, no longer being Catholic I don't adhere to the venal vs mortal sin idea. But, breaking the law, as far as I can tell is still sin. I understand perfectly why the Catholic church in the US has no trouble with illegal immigration, since it increases the numbers in their parishes. I don't think this is a particularly good reason to look the other way.