Of course Canada is free to sign any bilateral agreement with Mexico that she chooses...but I say no US/Mexico agreements.
I agree, the active invasion policy of Mexico has caused the deaths of far more Americans than Islamic Jihadists. Mexico presents a clear and present danger to the US national security and should be treated that way.
Their military is a threat; they use their military regularly to provide security and cover for drug shipments crossing the border. That alone should be considered an act of war each time they do it.
Mexico is not our friend in any way. They usually take great delight in voting against us in the U.N. or they did until President Trump was sworn in, now they abstain a lot. They are afraid he will cut off their money and stop the flood of drugs and illegals. They are afraid he will shut down the flow of money back to their country and return their poor, and their hardened criminals. They are afraid he will undo NAFTA and be able to coax companies into coming back.