Though I completely agree that our southern border is extremely porous, our northern border is more so. One of the recent gripes amongst US politicians seeking to fuel the 'War on Drugs' is the massive importation of high quality marijuana across the Canadian border. The mules basically hike through farmers fields in North Dakota, Montana, etc. to bring in large quantities of dope.

We actually attempt to protect the Mexican border because it is violated by illegal aliens so often, but sometimes I wonder why it would, necessarily, be the route of choice for terrorists. Why not just hike through a corn field? Maybe it's the connections they gain which offer them transportation and relocation opportunities when entering from Mexico that make that route the preferred method of entry, but from the south, with a guide, someone knows you're here. From the north, you enter undetected, though you have to make it on your own.

I think the southern border would be the best bet for them because most middle eastern terrorist look more like Mexicans than Canadians. They're smart enough to know the southern border only has about 11,000 border patrol agents covering 2,000 miles or so. A middle eastern person crossing the northern border would draw alot more attention than that same person crossing the southern border with a group of Mexican illegals. Even though there are only about 3,000 agents on the northern border which is longer, it would still be more difficult for terrorist to blend in crossing the border, or once accross, blend in with the general populace because the southern US states are mostly hispanic in the counties closest to the border and the northern border counties are not mostly hispanic.