National Review Online asked a group of commentators: "In the wake of September 11, it was often said that the attacks collectively changed us. Did it? Five years later, are we changed and how? Or, how should we have and didn't?" For all replies, see "Did It Change Us? 9/11, five years later."
9/11 changed much for conservatives, little for liberals.
Conservatives tend to see the United States, Western culture, and even civilization itself under assault from a barbaric totalitarian force in some way connected to Islam. They perceive a cosmic struggle — reminiscent of those in World War II and the Cold War — over the future destiny of mankind.
Liberals tend to have a far more relaxed view of the situation, as symbolized by John Kerry's 2004 comment calling terrorism a "nuisance" and comparing it to gambling and prostitution. Liberals widely accuse conservatives, for self-interested reasons, of exaggerating the threat. The hard Left goes further and purveys conspiracy theories about the Bush administration having perpetrated 9/11.
As I pointed out already in 1994 (in a National Review article), the current debate divides along lines closely mirroring those concerning the Soviet Union. Conservatives, being prouder of what Americans have created, worry more about external threats and urge confrontation; liberals, being more self-critical, are more sanguine, and prefer conciliation. Put differently, 9/11 mobilized conservatives against radical Islam even as it mobilized liberals against conservatives.
Looking ahead, nothing but an atrocity of terrible proportions will wake liberals and make "united we stand" once again a meaningful slogan. (September 11, 2006)