Snowden's case is different, officials say, because he disclosed how the government actually collects telephone and online information, leaving the NSA to try to reassemble its surveillance networks.
Justice Department and security officials have said that the surveillance programs were necessary to combat terrorist threats.
In an interview with CNN, Secretary of State John Kerry called Snowden "an individual who threatened this country and put Americans at risk."
"People may die as a consequence of what this man did," Kerry said. "It is possible the United States will be attacked because terrorists may now know how to protect themselves in some way or another, that they didn't know before."
In congressional testimony, NSA Deputy Director John Inglis said that Snowden's acts "constituted an irresponsible and real damage to the capabilities" of the NSA.
Former CIA chief Michael Hayden had some of the harshest language for Snowden. In a CNN op-ed, Hayden said that Snowden far eclipsed the damage that Manning caused.
"First, there is the undeniable operational effect of informing adversaries of American intelligence's tactics, techniques and procedures. Snowden's disclosures go beyond the "what" of a particular secret or source. He is busily revealing the "how" of American collection," Hayden wrote.
"...there are already reports of counter-terrorism targets changing their communications patterns. And I would lose all respect for China's Ministry of State Security and Russia's FSB if they have not already fully harvested Snowden's digital data trove."
Military law attorney Eugene Fidell told CNN that there is some good that can come of Snowden's leaking, though the former president of the National Institute of Military Justice is quick to add that he has little sympathy for Snowden.
His leaks helped lead to congressional hearings and a re-examination of how much intelligence gathering is appropriate and when it may be venturing into abusive territory.
"The public knowing, at least being aware, of the powers of the FISA court showed new and sweeping powers being exercised by the executive branch," Fidell said.
"This is a democratic country, a democratic society. An informed electorate is essential. Not every voter should know everything," he said. "But there is increasing concern across the political spectrum" that those powers may be overreaching.