Former U.S. Secretary of State Condoleezza Rice said Wednesday that the United States must remain vigilant in the fight in Afghanistan and help calm the drug battles along the Mexican border to help prevent the type of failed states that lead to more terrorism.

Rice delivered the keynote address to a crowd of more than 2,500 police and security professionals gathered in Anaheim for the 55th annual American Society for Industrial Security International Seminar, billed as the largest security expo in the world.

"Nothing has ever been the same since 9/11," she said.

Unless the U.S. leads the charge to stabilize Afghanistan and other volatile regions, "you can be assured you'll have (terrorist) attacks from there again," Rice said. "This is a long war, not a short one."

She emphasized that unpopular decisions may need to be made in order to bring about lasting peace.

"If you govern for today's headlines, you will not have history's judgment on your side," she said.

Rice, the first black woman to serve as secretary of state, served in that position from 2005 to January of this year, and previously served as national security adviser.

In March, she returned to Stanford University to teach political science, but maintains an active speaking schedule. (She is scheduled to return to Anaheim for the Produce Marketing Association's convention in two weeks.)

Rice said she's enjoying a break from international politics. "Not only can I sleep, but I can get up and read the newspaper and not need to do anything about what's in it," she said.

Rice spoke for about 30 minutes, then spent an additional 20 minutes answering presubmitted questions from the audience on subjects ranging from international politics to her mentors and her proudest accomplishments.

The biggest disappointment of her time as secretary of state, she said, is that she was unable to make more progress toward a two-state solution in the Middle East.

Asked what she is most proud of, she said: "I am most grateful - not most proud - that there was not another attack under our watch. And that we were able to defend this country in a way that allowed people to go back to their lives after 9/11."

Rice told the police officers and security professionals gathered at the conference that they are vital to maintaining safety every day at a local level.