Conversely, it is OUR responsibility to defend our borders - neither Canada nor Mexico are charged by their citizens or laws to protect a neighboring country. Treaties might promise mutual defense but when the attacker is a car load of un-profilible 'minorities' you can bet that PC and economics will win out over defense.
While I think it would be very eighborly of either Canada or Mexico to assist in this new type of defense, it is clear that neither wishes to yield the economic benefits of letting us go it alone -
So be it.
From today forward I will add the northern border to my short list of placed that need to be fortified. If some find it more difficult to get to walmart, and others have to pay a bit more for gas or cigarettes, if the occasional transient has to buy drugs, have liposuction, or have a baby on the 'wrong' side of a border, so be it.