While federal agencies like the FBI and the INS try to track the movements of shady terrorist organizations, the openness of American society -- and its celebrations -- puts most of the public safety burden on local police.
"The local law enforcement officers are often the ones who are on the scene," says counter-terrorism consultant Harry Brandon. "They're the ones who happen to notice the anomaly. They're the ones who stop the car and think there's something wrong."
It was a state trooper, not a federal agent, who arrested convicted mass killer Timothy McVeigh on a routine traffic stop after the Oklahoma City bombing.
For the traditional bash on New Year's Eve, New York's finest will institute some nontraditional safeguards: a "frozen zone" around Times Square, stripped of trash containers and parked cars; mailboxes locked.
In Seattle, 2,400 National Guardsmen will be available for duty in the event of trouble.
All the precautions and warnings have caused some security experts, like ex-FBI official Brandon, to believe international terrorists may be discouraged from staging an attack, while home-grown terrorists may see this as an opportunity.
"The millennium has become such a focal point and has been building up to this for a year," he says, "that lots of people may see it as their stage, including some who are just plain deranged."
Experts say that, if nothing else, all the talk about terrorism following the arrests of suspicious travelers on the U.S.-Canadian border has fully alerted local police agencies everywhere -- and they're the ones most likely to nab a terrorist before he can act.