In practical effect, we do.  Or at least did, until Trump decided to end the charade of "border-protection" that had been played out for the past 25 years under Clinton, Bush, and Obama.  

You attempt to make a point by saying that the majority of illegal immigrants are overstays. That hardly resolves the issue.  We have plenty enough of those who enter illegally.  

The only thing that can justify the situation we're in is that Christianity demands it. I am open to a rational discussion of this, but so far have heard none from you or the bishops, who are content to rest their entire argument on the premise that we must "welcome the stranger."  That alone doesn't suffice when the consequence could well be national suicide.  California's well on their way already.