Yet complacency seems to have crept slowly into American society in the past four and a half years as the terrorist attacks fade from our collective memory. Many fear that it will take another strike on U.S. soil to jolt Americans into action.

Anyone who sees United 93, however, will be jolted.

Painstaking research by writer-director Paul Greengrass ("Bourne Supremacy") is evident on-screen, culminating in a finished product that is perhaps the best educated guess as to what actually transpired on the plane that crashed into a Pennsylvania field instead of the Capitol. Mr. Greengrass and his crew interviewed members of the 9/11 Commission, government personnel who were directly involved that day, and over 100 family members of the 40 passengers and crew aboard flight 93.

Gripping, raw, and gut-wrenching are all words that have been used to describe United 93 in early reviews, and all fit. Yet as powerful and deeply affecting as the film is, it is hard to imagine any one movie making any discernible impression on the public consciousness.

The terrorist threat in 2006 is not likely lower than it was in 2001, yet many act as if the potential for suffering an attack here is as remote as most believed it was on September 10. Senate Minority Leader Harry Reid (D-NV) last year famously bragged that the Democrats had “killed the Patriot Act.” Around the same time, Democrats and even some Republicans spewed hyperbolic rhetoric about the NSA warrantless eavesdropping of individuals with direct or indirect ties to terror.

Reasonable people can disagree on the Patriot Act or the NSA eavesdropping, but no rational person can argue—as many Democrats did—that either represented a lethal threat to our liberties. We are at war. No, we have not been asked to ration, buy war bonds, register for a draft, or make any other major collective sacrifice. That doesn’t change the reality of what we face, but it probably does make it seem a little less real.

Reminders abound of how real this struggle is. Just this week, Hamid Hayat, a 23-year-old U.S. citizen of Pakistani origin, was convicted of material support for terrorism for traveling to his ancestral homeland to attend a terror training camp. This came just four months after the conviction of Abu Ali, the U.S. citizen who was the valedictorian of the Northern Virginia-based Saudi Academy, for plotting to assassinate President George W. Bush. Those are only the most recent cases.

In the past four and a half years, we’ve had terror arrests, deportations, and convictions across the country. The mainstream media has largely ignored most of these cases, meaning that those who know about them have sought out the information on the Internet or possibly talk radio. But the combination of lack of coverage about law enforcement’s success and the thankful lack of success by would-be terrorists has resulted in many Americans feeling less and less threatened. 9/11 just isn’t as salient anymore. Continued...