Twenty-five years after the attacks of September 11, 2001, the focus of U.S. counterterrorism efforts and presidential engagement with the legacy of that day have shifted significantly. While former presidents Bill Clinton, George W. Bush, Barack Obama, and current President Joseph R. Biden Jr. are scheduled to gather in New York to commemorate the anniversary at the World Trade Center site, former President Donald J. Trump will mark the occasion elsewhere, speaking at the Pentagon roughly 200 miles south.

The contrast in locations and commemorative practices reflects broader changes in how terrorism shapes American policy and politics. The four presidents attending the New York ceremony share experiences of governing during eras deeply influenced by the global war on terrorism, with their tenures marked by military engagements and national security priorities linked to the 9/11 attacks. By contrast, Mr. Trump, who was serving as a private citizen residing in New York on the day of the attacks, presides over an administration where foreign terrorism has receded from the forefront of the national security agenda.

During Mr. Trump’s tenure, definitions of terrorism have evolved to encompass a broader array of threats. His administration has designated drug cartels and transnational gangs as terrorist entities, prioritized combating left-wing extremism—including anarchist and antifascist groups—while critics argue it has downplayed or ignored the threat posed by right-wing extremist violence. The administration’s May 2023 counterterrorism strategy described the landscape as increasingly complex, citing “legacy Islamist terrorists,” narcoterrorists, and domestic violent extremists as principal concerns. This approach marks a departure from the post-9/11 focus on Islamist militant groups abroad.

Experts highlight that the shift reflects both the success of longstanding counterterrorism measures and changing threat perceptions. The fear of large-scale foreign terrorist attacks, which dominated the national agenda for years, has given way to concerns over domestic terrorism and random acts of violence, such as mass shootings. Surveys indicate that Americans now perceive domestic extremist violence as a greater threat than foreign terrorism. Additionally, most jihadist plots on U.S. soil since 9/11 have been carried out by individuals with little direct contact with international terrorist organizations.

Despite these changes, some scholars caution against complacency. Bruce Hoffman, a terrorism expert at Georgetown University, noted that the U.S. faces a more fragmented and diffuse terrorist landscape than in 2001, with threats from multiple groups including Al Qaeda, ISIS, Iranian-backed networks, and domestic extremists. He warned that stretching counterterrorism resources across expanding threat categories could dilute effectiveness.

Mr. Trump’s absence from the New York commemoration has drawn attention. Traditionally, no speeches are allowed at the 9/11 memorial site on the anniversary, a restriction reportedly influencing Mr. Trump’s decision to speak at the Pentagon instead. He has denied that this was the reason, stating only that he chose to participate at the Pentagon and did not provide further explanation for not attending both events. After his Pentagon remarks, Mr. Trump plans to depart the United States for a weekend at his golf club in Ireland.

Reflecting on the attacks from 25 years ago, Mr. Trump has often recounted his proximity to the World Trade Center on that day, though some of his claims about his actions then have been contested. During his presidency, he took a hardline stance on immigration from Muslim-majority countries and reinstated controversial interrogation techniques, signaling a distinct approach from previous administrations that sought to balance counterterrorism with religious inclusivity.

Major counterterrorism operations under Mr. Trump included the 2019 killing of Islamic State leader Abu Bakr al-Baghdadi and the assassination of Iranian Major General Qassim Suleimani, actions widely regarded as significant by security experts. The Trump administration also emphasized efforts to secure the release of hostages held by terrorist groups, a focus that has earned commendation even from some critics.

While the U.S. has largely redefined its terrorism policy in the years following 9/11, the question remains whether the current approach adequately addresses the diverse and evolving nature of threats. As counterterrorism institutions have faced budget cuts and restructuring, some analysts express concern about diminished institutional expertise and preparedness. Whether the evolution of the terrorism challenge will leave the nation more vulnerable or better protected is a question that experts say only time will answer.