Yes, but unfortunately the two largest enclaves for the Islamic fundamentalists are in Canada, each within a few miles of our northern borders. None of them in Mexico, Central and South American come close in size and organization as those two. So far we haven't been too successful in getting Canada to cooperate with us in issues regarding those centers.
"The reason for the southern focus is the 2 million plus folks that sneak in undetected, which is far less then the few thousand that sneak in undetected up north. The biggest hole gets the most attention."
Actually the biggest hole is the Canadian border, not just in physical size but in visibility and levels of protection; the southern border just had the greatest flow of illegal immigrants. This is knowledge that our Islamic enemies well know...why try to sneak explosives in on the most protected border when they have so many miles of open borders just a few miles away.
Because it's easier to operate in the corrupt environment of Mexico, then in Canada. Also, Canada actually tries to stop folks from crossing into the US illegally, while Mexico encourages and helps anyone and everyone in their attempt to enter the US illegally.
And no, I'm not trying to down play the importance of securing our northern border.