Did the people who were in the Americas when the Europeans arrived themselves encounter people who proceeded them when they arrived? If it was unpopulated virgin land then it doesn't matter whence they came. Unless they displaced Lizard people or something, in which case I expect descendants of Lizard People will soon come forth and demand reparations of American Indians.
Grab a history book. “Native” tribes moved among all of the Americas, conquering what ever other “native” tribes were on the land that they wanted. Conquering was usually violent and permanent, as has been forever in time.
That doesn’t mean a country can’t or shouldn’t control its borders, and admit people who serve its purposes, not the purposes of the aliens.
Virtually every other country in the world controls its borders better than the US. Why is that? It’s because we have people in control who wish to subvert the US for their own gain in power (democrats) or money (republicans), all while Joe Citizen sits on the couch, hoping they die before this self-inflicted invasion comes to their doors.