WASHINGTON — Americans are destined to worry about terrorism approximately forever.

Five years after that blue-sky Tuesday turned dark with death and rubble, longer now than the U.S. fought in each world war of the last century, the essential characteristics of the terrorists haven't changed, nor the nature of the confrontation. No treaty is possible, no truce to be had, no Mission Accomplished banner contemplated as far ahead as anyone can see.

The terrorists are endlessly sneaky, clever in some ways, almost comically bumbling in others, and seemingly replenished as fast as they can be killed or captured. Hopelessly outmatched in any head-to-head confrontation, but impossible to stomp out. And always lethal because it only takes a few with a brain wave, or one with a strapped-on bomb, to cause mass death.

Five years after the Sept. 11, 2001, attacks, the government says it lives every day like it's Sept. 12, 2001. That's an exaggeration — the country is not on highest alert — but there are, at least, both visible and invisible sentries at work always.

Combat air patrols comb the skies with new post-9/11 powers to shoot down civilian aircraft. They've logged more than 42,000 flights. Ships at sea prowl for incoming dangers with new authority to intercept suspicious vessels. Unseen eyes monitor movements and communications in ways that have never been.

The government's squishy mantra: Safer but not safe.

Expect never to hear this: We're safe. Relax.

There are indications Americans are taking a fork in the road when it comes to the impact of the threat on their lives. At first, everyone walked on eggshells.

Now, AP polling loosely finds two levels of worry based on where people live. More than half of the people in New York and Washington are concerned about their cities being attacked, polling suggests. Less than one third of Americans overall have this concern about where they live.

But half the people surveyed both in targeted cities and nationally say the attacks changed the way they live to this day. And most worried that the war in Iraq has made a terrorist attack on the U.S. more likely.

Absent another attack, a low-grade disquiet persists, one that spiked up when the British foiled the alleged plot to blow up U.S.-bound airliners in the sky. Americans boarding airplanes scan seat-mates and make snap judgments of character.

Anything suspicious trips a hair-trigger sensitivity. Nearly one in five Americans polled for AP reported suspicious activities or people in recent months.