One of the aspects of the 9/11 attacks less mentioned in the mainstream media is that the attacks could not have happened without lax American immigration policies. Many of the terrorists who attacked us were here illegally. This was due not to crossing the border illegally, but rather overstaying visas or misrepresenting themselves on visa applications. Others were here legally who never should have been.
Mohamed Atta, ringleader of the attacks, was stopped in Florida and found to be driving without a licence. His immigration status was unquestioned. A warrant was issued for his arrest, but this didn't stop him from flying around the county, and to Spain and back.
Adding insult to injury, Atta and another hijacker were issued visas six months after the attacks.
Outrageously, while our foreign policy has been widely debated, very little has been done to fix our immigration policy. The government refuses to do so.