The war abroad has made defense at home an even more urgent priority, but the rising cost of security is sparking squabbles at all levels of government.
States and cities are faced with the burden of stronger homeland defense at a time when their finances are in the worst shape of the last half-century.
State troopers in Connecticut keep watch from the sky 24 hours a day, guarding reservoirs, bridges and more; National Guard troops in Arizona patrol the biggest U.S. nuclear power plant; safety worries shut Philadelphia's Independence Hall most of last week.
No overall, national figure for the cost of such measures to both cities and states is available, though partial estimates reach well into the tens of millions of dollars per week.
"Everybody's budget is hurting," said Baltimore Mayor Martin O'Malley. "This just whacks the heck out of it."
Security officials pledge that, come what may, they will redirect resources to keep the country safe. But the strain is obvious.
New York Gov. George Pataki sparred publicly with New York City Mayor Mike Bloomberg over how they'll share a still-evolving infusion of federal funds for security.
Elsewhere, governors are telling Congress they should get control of federal security funds, while mayors argue they are closest to first-responders - the police, fire and emergency crews that would deal most directly with terrorist activity.
Congress is working on a war budget that would add more than $4 billion for homeland security, including upward of $600 million for urban areas considered higher threats. And Homeland Security Director Tom Ridge has emphasized that state and local authorities are crucial.
"This war is being fought on two fronts," Ridge said in Florida as Week 2 of the Iraq campaign began. "There is a theater over there and a theater right here."
That was driven home when Iraqi leaders called for jihad and warned of suicide bombers that would "follow the enemy into its land."
Two days before the first bombs fell on Baghdad, the U.S. security alert went to orange, or high. Immediate changes followed.
National Guard troops were called up to patrol in many states, performing tasks such as watching state ports on the Gulf of Mexico and the Mississippi River, and protecting water supplies in Minnesota.
Black Hawk helicopters patrol above New York City, metal detectors check visitors at Rhode Island's statehouse, and Missouri Gov. Bob Holden has plans for a system to track bioterrorism and disease outbreaks in his state.
Los Angeles Police Chief William Bratton asked his city council for $4.5 million for biohazard suits and equipment, arguing that they couldn't wait for federal help.
"There's a lack of confidence that the federal money is coming anytime soon," Bratton said. "By the time it gets down to the states, then to the county and then to the city, we could be into the next war."
In several states, homeland security officials are keeping track of their spending in hopes that the federal government will pay them back later.
"There may be dollars that come back to relieve their pain," said Wisconsin's emergency management director, Ed Gleason, "and there will be pain."
The cost of all these efforts is tough to pin down.
Nationwide, some $21.4 million was being spent each week by 145 of the largest cities, towns and counties, according to a survey by the U.S. Conference of Mayors. But they estimate the total cost for cities could be $70 million a week.
No similar tally of state costs has yet been made.
Ridge maintains that the states will get upward of $8 billion when everything is accounted for in President Bush's several spending requests since Sept. 11.
Others say that falls far short. Cities have yet to be reimbursed for $3 billion in expenses; water system vulnerability assessments are estimated to cost $900 million; and much of the $3.5 billion in last year's federal budget was just a reallocation of previously designated funds, according to Federal Funds Information for States, a Washington data clearinghouse.
The fight over money will continue, even as homeland defenders adapt to their new tasks.
"America's different. The America that you and I knew pre-Sept. 11 is different," said Sheriff Joe Oxley in New Jersey's Monmouth County. "We're going to have to adapt and be fluid."