As the U.S. marks 15 years since nearly 3,000 people were killed in the worst terror attack on American soil, at least one foreign affairs expert says the country is safer than it was prior to 9/11.

Sunday marks 15 years since terrorists killed thousands in co-ordinated attacks on the World Trade Center in New York City, as well as at the Pentagon in Virginia and a hijacked plane that crashed in Pennsylvania. The attack launched the country and the world into the war on terror. Since then, the U.S. has spent an estimated US$1 trillion on security.

Shuvaloy Majumdar, a Munk Senior Fellow at the Macdonald-Laurier Institute, says the U.S. is safer “as a result of a decade and a half of investing in a new security threat.”

Prior to 9/11, the world had become accustomed to warfare on open battlefields and state-to-state combat, Majumdar said in an interview with CTV’s Your Morning on Friday.

“But after 9/11, it became evident that the threat to western society, to the United States, really hinged on our ability to adapt to asymmetric threats -- those posed by terrorists, or hybrid warriors who don’t necessarily operate on the terrain of battlefields that we’ve become accustomed to,” he said.

In the U.S., as well as other parts of western civilization, a lot of investment has gone into “creating communications” between military and domestic security systems, in order to confront a “very, very bold threat,” Majumdar said.

Localized threat

In the immediate aftermath of 9/11, the threat prevention focused on “spectacular” attacks on major buildings, infrastructure and symbolic sites.

But now the threat profile is “mutating,” Majumdar said.

“What we’re seeing now, after the long interventions in both Iraq and Afghanistan, is the threat is taking on a much more local character, with lone wolves, self-radicalized individuals, gunmen trying to disrupt peace and order in small cities.”

The homegrown threats are “invisible” to security forces and therefore harder to track.

Majumdar points to the recent spate of bombings in Europe, and the “lone wolf” attacks on Parliament Hill in 2014, and more recently, at a gay nightclub in Florida.

“The threat is perpetual, and I think it would be a bit naïve to presume that it has diminished or gone away altogether,” he said.

However, he says a lot of investments have gone into successfully confronting the foreign threat.

“More work needs to be done, but invariably, we are safer today, 15 years after 9/11, than we were before,” Majumdar said.

P.J. Crowley, a former U.S. assistant secretary of state, said citizens have “adjusted a lot about how we live” following the 9/11 attacks.

“Obviously any of us who travel on an airplane these days, that experience is much different than it was then,” Crowley told CTV News Channel on Friday.

Balancing privacy and security is also an ongoing issue that has affected Americans’ day-to-day lives.

Crowley said, since 9/11, the world “is a more dangerous place, but terrorism is only one of those factors.”

He cited the spread of global health problems, such as Zika and Ebola, as examples of other issues facing the global community.

“I think we live in a very complex time,” he said.

Crowley added, it’s important to recognize the danger of terrorism, while keeping it in its proper context.

Most Americans, he said, are “more likely to hit by a bus” than be killed by terrorists.