Here are a few excerpts that mention immigration, borders, or visas:

Page 213
Between late March and September 2001, the Intelligence Community identified numerous signs of an impending terrorist attack, some of which pointed specifically to the United States as a target:
...In May, the Intelligence Community obtained a report that Bin Ladin supporters were planning to infiltrate the United States by way of Canada to carry out a terrorist operation using high explosives. This report mentioned without specifics an attack within the United States. In July, this information was shared with the FBI, the Immigration and Naturalization Service, the Customs Service, and the State Department and was included in an intelligence report for senior government officials in August.

ADDITIONAL VIEWS OF REPRESENTATIVE MIKE CASTLE (R-DELAWARE)
...The State Department's Bureau of Consular Affairs and the Justice Department's Immigration and Naturalization Service have joint responsibility for the management of our visa program, yet this program's administration has been characterized by poor management practices, uneven enforcement policies, and inadequate coordination between these agencies and other elements of the U.S. intelligence and law enforcement communities. The majority of theSeptember 11th hijackers were wrongly admitted to the United States -- in violation of U.S. immigration laws -- as a result of decisions made and errors committed by responsible State Department and Justice Department officers. The fact that many of them entered and operated in true name, further emphasizes the extent to which the current system is broken...

...I strongly believe that significant legislative changes are urgently needed to redirect and reorganize our national visa policies.

JOINT INQUIRY STAFF REPORT/ADDITIONAL VIEWS/SENATOR JON KYL, SENATOR PAT ROBERTS
...The failures that led to 9/11 occurred not only in the intelligence community. The JIS was selective about what threads of inquiry it was willing to follow beyond the intelligence community. Failure to examine the State Department's visa-issuance process must rank as the most glaring of these omissions because the answer to the question — could 9/11 have been prevented -- is yes, if State Department personnel had merely followed the law and not granted non-immigrant visas to 15 of the 19 hijackers in Saudi Arabia.

We repeat: If our own laws regarding the issuance of visas had been followed by the State Department, most of the hijackers would not have been able to obtain visas, and 9/11 would not have happened. Because the entire culture of the State Department is geared toward facilitating smooth relations with foreign governments, State Department personnel have tended to ignore the potential effect of their practices on national security.

EXECUTIVE SUMMARY
(link) Neither the State Department's consular officers nor the Immigration and Naturalization Service's agents and inspectors were ever considered full partners in a national counterterrorism effort. Protecting borders was not a national security issue before 9/11...

(link) ...Set standards for the issuance of birth certificates and sources of identification, such as driver's licenses.

See, for example, the earlier post "Congressman: Terrorists are infiltrating the U.S. via Mexico". Due to political correctness and a desire for serf labor, are we doing all we can to prevent another attack?