But as President Obama prepares to send the United States on what could be a yearslong military campaign against the militant group, American intelligence agencies have concluded that it poses no immediate threat to the United States. Some officials and terrorism experts believe that the actual danger posed by ISIS has been distorted in hours of television punditry and alarmist statements by politicians, and that there has been little substantive public debate about the unintended consequences of expanding American military action in the Middle East.

Daniel Benjamin, who served as the State Department’s top counterterrorism adviser during Mr. Obama’s first term, said the public discussion about the ISIS threat has been a “farce,” with “members of the cabinet and top military officers all over the place describing the threat in lurid terms that are not justified.”

“It’s hard to imagine a better indication of the ability of elected officials and TV talking heads to spin the public into a panic, with claims that the nation is honeycombed with sleeper cells, that operatives are streaming across the border into Texas or that the group will soon be spraying Ebola virus on mass transit systems — all on the basis of no corroborated information,” said Mr. Benjamin, who is now a scholar at Dartmouth College.