I know a lot of you on this site aren't Americans. I have a question for you: notwithstanding the whole "European Union" relaxation of borders for purposes of stimulating trade and travel within said Union, how do you feel about your national sovereignty and security? A lot of European nations have been having to deal with a torrent of immigration from third world countries for the past few years, and they are finding out first hand that it's no picnic in the park.
The US has been dealing with such a torrent for decades, and it's reached the point that immigrants feel entitled to the same rights and privileges that we have as Americans, without assimilating, without abiding by our laws, without paying taxes into the system, even when they receive the benefits (free education, public assistance, Medicaid) paid for by those same taxes.
We've got sh*t going down like MS13 gang members literally kidnapping two girls on their way to school, raping and murdering them, and dipsh*ts in NY and DC acting like they didn't do anything wrong, and they are somehow victims by being arrested for their terrible crimes!
People are getting trafficked in by the literal TruckLoad over our overly-porous border, being victimized, left to die, and sold into slavery in factory farms and the sex-trade and as servants for the well-to-do. What we have now is NOT WORKING, and if building a wall will help to even slow the pace of this wretched phenomenon, I say build that freaking WALL as high and as long and as deep as you can.
If Canada, Mexico, Great Britain, Australia, and every other country can choose who they do and do not let into their country, why shouldn't we exercise the same national right? Because we're American? Because those profiting off of the sale of the drugs and the guns and the humans like it better this way? Because our politicians tell us we should each be carrying around a great big bag of "white guilt"?
Nope, nope, and nope. It's the Land of the Free, not the Land of the Free-for-All.
P.S. Your flimsy "careful what you wish for" argument is ridiculous. If the govt. or some other entity ever tries something to make us want to leave, not only will they fail, but they will awaken a sense of purpose and cooperation in us that hasn't been seen since WWII. And we all know how that worked out.