If people are determined to get into this country, they will find a way. We can't wall off the country and stay protected inside it, like too many people do today sitting in their houses inside gated communities. That practice sets an example of isolationism that we cannot afford in today's world.
We are part of the rest of the world and we are all interdependent.
It reminds me of the Edgar Allen Poe story, "The Masque of the Red Death," where the prince and his favorites decided they could avoid the plague by walling themselves off and living a continual party while the people were dying outside the walls. Death found its way in anyway.
We need to be part of the solution, and that requires accepting diversity - in culture, in religion, and in race.