[Aria]

I think it’s rather that Bush is focused on the war on terror, and this doesn’t show on his radar.

Terrorists can sneak across the border along with the Mexicans - in fact I'd be willing to bet that they've done this.

[GAB-1955]

Maybe. However, the 9/11 terrorists came into this country legitimately. The London bombers came into Britain legitimately. Seriously, if you are going to have a longterm sleeper cell, you don't want them to be picked up on immigration charges until they have carried out the mission. As in espionage, it's better to have legal cover.

This is not to say it can't happen or it hasn't happened, but it depends on the quality of the terrorist.