In response to your “re.” line, it depends on the laws.
Laws that are inherently unjust because they are based on ethnic, religious, gender, or race quotas? Or laws that merely attempt to prevent the influx of criminals or people with communicable diseases?
"2241 The more prosperous nations are obliged, to the extent they are able, to welcome the foreigner in search of the security and the means of livelihood which he cannot find in his country of origin. Public authorities should see to it that the natural right is respected that places a guest under the protection of those who receive him.
Political authorities, for the sake of the common good for which they are responsible, may make the exercise of the right to immigrate subject to various juridical conditions, especially with regard to the immigrants’ duties toward their country of adoption. Immigrants are obliged to respect with gratitude the material and spiritual heritage of the country that receives them, to obey its laws and to assist in carrying civic burdens."
Catechism of the Catholic Church
I think we need to ask ourselves, when you weigh the benefits and burdens, to both our “infrastructure” and “economy” against those of the individuals who seek entry, what is the Christian thing to do?
"Give me your tired, your poor,
Your huddled masses yearning to breathe free,
The wretched refuse of your teeming shore.
Send these, the homeless, tempest-tost to me."
Are we still this country or have become something else, something . . . less?