Fifteen years after 9/11 attacks, is America any safer?

On September 10, 2001, then-Attorney General John Ashcroft rejected an FBI request to increase the anti-terror budget. Also on that day, FBI officials testified in Congress that the biggest terrorism threat in the nation was from animal rights activists.

But what happened just one day later changed the nation. Since the 9/11 attacks, the United States has spent an estimated $1 trillion on security and defenses against terrorism. But has that made America any safer?

As we approach the 15th anniversary of the attacks next month, author Steven Brill looked at how the U.S. has confronted the threat of terrorism in a new article for the September issue of The Atlantic magazine entitled, "Is America Any Safer?"

After a year of investigating, Brill concludes in his cover story that "we are not safer."

"We've done a lot of things to make us safer. There are tens of thousands of men and women who wake up every morning for the last 15 years doing yeoman's work, trying to keep us safer," Brill told "CBS This Morning" Wednesday. "But the kind of threats we face ... have expanded."

Additional layers of security - like checking airline passengers against watch lists, airport surveillance, checking for ID and dangerous materials, and fortified cockpit doors - have improved our defenses against the specific type of attack America faced that September morning. But according to Brill, the kinds of threats we face today have "multiplied." He says "orchestrated" attacks such as those using bioterror or a "dirty bomb" remain hard to detect.

"Someone can go into a hospital and steal some radiological material very easily and mix it over the standard explosive and create a bomb that causes radiation contamination ... that will scare the country so much that we may have to evacuate a large portion of lower Manhattan or Washington," Brill explained. Another example he offered: "There's the lone wolf who can go into a gun store, uniquely in this country, and buy an assault rifle and shoot up a shopping mall or theater, and if he yells out an expression in Arabic, we assume that that's a terror attack."

He pointed out that more Americans die from gun violence than terrorism, but "terrorism is about fear, and that's what makes it such a force in this country."

The morning after the 9/11 attacks, President Bush directed Ashcroft to make sure "this can't happen again." While Brill called this a "fantasy," he said Bush's remark was "understandable" at the time.

He praised both the Bush and Obama administrations for doing "a very good job of 'standing up' the country" to deal with the threat, and noted, "We really have to take our hats off to people who wake up every day at the Department of Homeland Security, the TSA - who, you know, we love to ridicule and make fun of - who have been obsessed with keeping us safe."

But Brill is concerned about the rhetoric being used in this year's presidential campaign.

"The idea that someone can say, you know, 'I'm running for president and I'm going to declare war on Islam and the day I take office, all of this is going to stop,' is just ridiculous," Brill said. "I don't want to engage in partisan politics, but it doesn't take a genius to figure out that the terrorists would love to have someone like a Donald Trump to be the president of the Untied States because he is willing to declare war on all Islam and that's the way they have framed the issue since September 11th. President Bush refused to take that bait, and President Obama has refused to take that bait."

Instead, Brill said the U.S. should accept the "fact that 'never again' is a fantasy" when it comes to terrorism, and instead take appropriate measures to deal with the existing threats such as bioterror or a dirty bomb.

"What that entails is the president of the United States getting at the bully pulpit and saying that this bomb is scarier than it actually is. It's not as dangerous, it just - it's meant to scare people," Brill said. "The reaction is what's really bad."