You must separate between personal interest and valid government interest. The federal government is legally bound by the Constitution, the ONLY legal source of its authority and action.
Nations are sovereign and must not meddle with each other unless there is imminent danger one to another.
If you want to personally see about helping these people fine. But the federal government is bound by the Constitution to “protect every state” from invasion (Art. IV, Sec. 4) and illegal immigration is invasion.
Right. The Federal government is not a Unitary government.
You seem to dance around this question.
What do you think of State Patrol at ports of entry, keeping hordes of unemployed vagrants out? Is that “legal” or “constitutional”?