Concern is often expressed about our security in light of the high influx of undocumented immigrants from our southern border.
While unauthorized immigration is problematic, framing it as a security issue highlights the concerns. Hence, one needs to know if those are valid concerns, or if they are smoke screens.
Looking at the map, one may notice that our borders with Canada run about three times the length of our southern border. Therefore, if one is concerned about terrorists coming in from the south, why not have similar concerns about the northern border? If we need to build a fence in the name of national security at our southern border, why not build one at the lengthier northern border as well?
Indeed, security-wise, our Canadian border should raise more concerns. Not only is it much longer, but it is also less guarded and does not involve a hard-to-cross desert. Just as important, in the countries the terrorists are likely to come from (such as those represented in the 9/11 attack), English is spoken and taught as a second language. In contrast, Spanish is almost never taught nor spoken in the Middle East. Hence, it would be logistically much easier for terrorists to sneak through our borders via Canada than Mexico.
Of course, we neither want to surround ourselves with fences, nor live in a cage. But, I suspect the reason no one has suggested a fence along our Canadian borders is that the security concern is a smoke screen intended to add fear to what is primarily an immigration issue. Ironically, the best way to protect us from terrorists coming from any border is to streamline the entry of needed workforce, so that they would not need to cross illegally. Once we achieve that, those who would then need to cross can be identified easily. Since there will be less incentive for legitimate workers to enter illegally, we can then assume that those who would attempt to enter illegally might be the really bad guys.