Regardless, a wall is not necessary to stop terrorists from coming into the US. Even the report you cited noted that CBP figures for fiscal year 2010 indicate that 447,731 illegal crossers were apprehended along the southwest border and 7,431 along the U.S.-Canada border.
No serious person suggests we build a wall on our Northern border. Can you cite anyone who recommends that?
Ah yeah that is the point. They effectively control 32 miles of the 4000 mile Northern Border which means they would have way less illegals apprehended. And, the same report tells us that more terrorists cross the Northern border.
And we have not even talked about the Illegal Drug Trade. Bottom Line closing the Southern Border and leaving the Northern Border open will reduce illegals crossing the Southern Border but then more will cross the Northern Border and along with drug mules and the bad guys etc.
Can you give us a good reason to not build a wall on the Northern Border? And no "cost" is not a good reason. Stopping nefarious nutters the ability to wander over the line anytime they please is worth every penny we would spend on building the wall.