Canada has taken in thousands of Middle Eastern refugees and has vastly more Arabs and Muslims than Mexico. The odds of a Middle Eastern terrorist entering the US would be much higher on the Canadian border than the Mexican border. The fact is, one hasn't entered the US through either border. The argument is being made for tighter security on the Mexican border because a terrorist, most likely Muslim or Arab, will just walk across the border. That isn't even an issue. It's prioritizing imaginary crimes and fear mongering. The same people who have this concern of terrorists walking across the border don't always share that concern for the northern border. It's just a diversion for their real concern.