I think that a very strong argument can be made that one of the most painful casualties of the September 11 Attacks was immigration reform and the perception of the immigration issue. The instant level of fear that gripped America in the days, months, and years following September 11 was manifest by a broad based shut down of immigration, losing a source of national strength. Immigration once again came to be viewed as something that needed to be limited and controlled. Many became convinced of this in noting how easy it was for the hijackers to obtain student and travel visas in the period leading up to the September 11 Attacks. The focus of the nation was driven on placing regulations and restrictions on immigration, in the belief that greater security would result from stemming the number of those who enter the nation.
The War on Terror enhanced this. In the belief that the enemy could "be anywhere," a logical extension of this was that immigration could be used as a cover for those who wished to do the nation harm. The earlier progressive discussion on immigration was tabled and then it regressed. This is significant because prior to September 11, President Bush and Mexican President Vicente Fox were working towards an approach that would allow a path for citizenship and help to create a dual nation approach to immigration that was seen as inclusive and compassionate.
This endeavor was tabled after the September 11 Attacks. We need only see how the immigration issue is so divisive and thorny a political topic to be reminded of how the War on Terror influenced the way the American political leaders have treated it and how the American people are divided on it. In this confusion, one sees that the War on Terror has significantly influenced the nation's ideas on the immigration issue.