The proponents of completely unfettered immigration make the often-strident demand that those who disagree with them provide scriptural support for their position. While I can easily provide such support (if given the chance without being personally abused to no end while attempting it), in fact the burden of proof is on them to prove their extremely radical, revolutionary, functionally-internationalist proposition.
The right and duty to defend life, liberty, and private property, to protect ourselves, our families, our communities, and our nation, is self-evident and intrinsic, and has always been understood to be so, throughout the history of mankind, throughout the history of western Christendom, and, most particularly, throughout our own national history.
In 1772, Samuel Adams rightly called this intrinsic right and duty "evident branches of, rather than deductions from, the duty of self-preservation, commonly called the first law of nature."
When God commanded "you shall not steal," He used the negative to highlight the positive fact that He had endowed men with private property rights.
When God created the nations, and marked out their times and territorial extent, He didn't suddenly decide that it is permissible to steal, as long as you do it on a grand, national scale.
Generally-speaking, nations are bodies of people who share a natural common bond of heritage and history, of language, of manners, of religion, of political, economic, and security interests, and of physical territory.
As a sovereign body of individuals who have joined themselves together, those nations have a right to defend themselves, and, in the interest of the weak and helpless among them, and in the interest of their own posterity, have an intrinsic duty to do so.
And that necessary nationalistic, self-protective, defensive function, which was appointed by God Himself, shall not cease until the Lord Himself returns to rule and reign personally.
It's not a perfect system, not by a long shot, governed as it is by weak, sinful men. It's very messy and deeply flawed, even in the best cases. But it is one of the necessary, God-instituted restraints on evil in this fallen world full of fallen men.
Remove those restraints, remove those moral boundaries, remove those physical borders, and the only thing that can ensue is destruction.
"The God who made the world and everything in it is the Lord of heaven and earth...From one man he made all the nations, that they should inhabit the whole earth; and he marked out their appointed times in history and the boundaries of their lands. God did this so that they would seek him and perhaps reach out for him and find him, though he is not far from any one of us. ‘For in him we live and move and have our being...'"
-- Acts 17:24-28
Stop trying to undo what God did. Providentially, this amazing American republic exists, for your own protection and the protection of your children and grandchildren. Defend it. Don't blithely turn your heritage, and the heritage of your earthly posterity, over to those who would invade and destroy us.
We know from scripture that in the end of history, all of God's restraints on men will finally be broken down, to their mass destruction. But, in the meantime, America can continue to be a peaceful place for men and women to seek the Lord, to take care of their families, and can still serve as the wonderful platform it has been throughout the last several centuries to take the gospel to the rest of the world. Inevitably, its destruction must someday come, but Christians should not be willing agents of that destruction. They should instead help ensure its preservation as long as they possibly can.