Washington D.C. (CNA/EWTN News) -- On the 15th anniversary of the World Trade Center terror attacks, we shouldn't overlook how Middle Eastern Christians have suffered from the unintended consequences of U.S. post-9/11 foreign policy, says one expert.

"The U.S. Catholic bishops, in their statement after the Sept.11 attacks, made it clear that the response has to be a response that brings more peace for all, not just greater security for U.S. citizens," said Maryann Cusimano Love, an international relations professor at the Catholic University of America.

U.S. Catholics must see themselves as part of "a global Church, and that as followers of Christ, the Prince of Peace, He came to bring peace for all, not for a narrow band," she told CNA.

The day marked the 15th anniversary of the Sept. 11 terror attacks, when 19 men affiliated with the terror group Al-Qaeda hijacked four commercial flights and directed three of the airplanes straight into the two World Trade Center buildings in Manhattan and the Pentagon in Washington, D.C.

The fourth hijacked flight crashed near Somerset, Pa. and was reportedly headed for the U.S. Capitol building. Almost 3,000 perished in the attacks.

In response, the U.S. began the "War on Terror" shortly after with the invasion of Afghanistan to defeat the Talibanin 2001, and then the War in Iraq in March, 2003.

At the time of the Sept. 11 attacks that were motivated in part by religious extremism, the U.S. was not able to properly grapple with the role of religion in international affairs, Love explained. Since then it has struggled to engage with religious actors in the right way.

"The U.S. government was pretty much blind in being able to deal with religious actors or religious factors in foreign policy," she said of the time of the attacks.

"Our foreign policy organizations were primarily built to fight the Cold War. And in a fight against 'godless Communists'," she added, "you really didn't need to understand religion that much."

After the attacks, U.S. foreign policy swung to the opposite extreme to viewing religious actors "only as a problem" and a "source of conflict," she added.

Thus, "it's really taken a long time," she said, to help those crafting U.S. foreign policy "to understand that religious actors can be a positive force in international politics for peace, for prosperity, for development, and not only or merely a source of conflict."

Middle Eastern Christians and other religious minorities have also suffered greatly from the unintended consequences of U.S. post-9/11 foreign policy, despite the ultimately-prophetic warnings from Catholic leaders, including Pope St. John Paul II, against the War in Iraq, Love explained.

"Christians in the Middle East are in a fight for their lives," she said, and "in a large part the U.S. response to the Sept. 11 attacks certainly played a role in that."

With the war beginning in 2003, attacks on Iraqi Christian communities increased and Christians left the country. While over 1.5 million Christians lived in Iraq in 2003, there are fewer than 500,000 now.

Also, militant groups like al-Qaeda in Iraq and the Islamic State of Iraq and Syria -- which did not exist at the time of the U.S. invasion -- came into Iraq, Love noted.

"One thing many Iraqi Christians will tell you, they had no love for Saddam Hussein, but they all point to that as a golden age, that their lives were so much better under that regime than they are now," she said. "They said then we had one brutal dictator to worry about; now we have many. And the sources of instability are much larger, much wider. And they're under threat from many more corridors."

Moving forward, U.S. policy must take all religious actors -- the good as well as the bad -- into account, Love insisted.

"The U.S. foreign policy has always been created around governments, countries, states," she said. "Yet that form is really recent. Most countries in the world today are between 25 and 50 years old." And the services many countries boast of having -- education and health care, for example -- have been provided by religious actors for millennia.

And the positive stories of religious leaders must be highlighted, she said, in countries like Columbia, the Philippines, and Central African Republic where they are "risking their lives" to promote peace.

The U.S. must also remember that the universality of the Catholic faith, where members of every country and continent are Christian, as opposed to other faiths that are more geographically concentrated.

"That's still the growing edge for U.S. foreign policy, to understand the depth and the breadth that religious actors bring to these issues and the positive contributions they can bring," Love said.