WASHINGTON — Law enforcement agencies must improve their information sharing and avoid pandering to political correctness if they wish to prevent future terrorist acts on U.S. soil, officials told the House Homeland Security Committee Wednesday.

“At the start of the War on Terror—the enemy was clear and in plain sight,” said Bruce Hoffman, director of the Center for Peace and Security Studies at Georgetown University. “Our challenge today is to recognize the amorphous, diffuse and individualized threat.”

A panel of experts, including former New York mayor Rudy Giuliani, warned the committee that America’s ability to fully combat domestic terrorism could be compromised by a lack of cohesiveness within the law enforcement hierarchy. The witnesses cited missed signals and poor communication prior to the Boston Marathon bombings; the 2009 attack on a military recruiting office in Little Rock, Ark., and the Fort Hood massacre.

“We can no longer deal with this by not sharing information or there will be other Bostons,” said Giuliani, who served as mayor of New York City during the 9/11 attacks.

One of the largest challenges for U.S. intelligence today, the panel agreed, is identifying potential threats – especially the radicalization of individuals — as early as possible.

“The shift from radicalization to mobilization is difficult to detect,” said Michael Leiter, the former director of the National Counterterrorism Center. “We have to train local officials so they can recognize the signs.”

Leiter and Giuliani said the U.S. must learn from its past mistakes, including when numerous government officials overlooked Maj. Nidal Hasan’s unusual behavior in the months leading up to the Fort Hood massacre.

A 2011 Senate Homeland Security Committee report noted that prior to the Fort Hood shootings, government officials were aware of Hasan’s embrace of violent Islam while on active duty. The report also revealed that signs of Hasan’s increasing radicalization were “sanitized” in his Officer Evaluation Reports – referred to as alleged research on Islamic extremism.

The FBI later cited those affirmative evaluation reports when it dismissed the need for additional investigation into some of Hasan’s communications.

FBI officials refused requests to testify in front of the House committee on Wednesday.

“Since 9/11, the vast challenge to our security apparatus remains connecting the dots,” said Committee Chairman Mike McCaul, R-Texas. “A failure to share information is now being witnessed in this room.”

Rep. Peter T. King, R-N.Y., expressed similar feelings, saying, “the FBI has a lot to explain. The fact that they are not sharing information is totally unacceptable.”

The committee and panel also cited the Fort Hood massacre as evidence that term “terrorist” has become a buzzword in the U.S. and political correctness is hindering the nation’s ability to properly identify terrorists.

“Our inability to define the threat because of political correctness poses a danger to the safety of Americans,” said McCaul.

The shootings at Fort Hood have not been designated as a terrorist act. The incident, which claimed 13 lives, is still officially called “workplace violence” — a designation that is preventing those killed or injured from receiving Purple Hearts. A March 2013 Defense Department paper stated that the military opposes awarding the medals to the Fort Hood victims, in part, because that could compromise Hasan’s Sixth Amendment rights to a fair trial.

Giuliani and others called the workplace violence label outlandish and dangerous.

“It is exceedingly damaging to say that Maj. Hasan engaged in workplace violence at Fort Hood,” said Rep. Sheila Jackson Lee, D-Texas. “It was so obvious that this man was a terrorist.”