Releasing an advance copy of his speech to Columbia University's Graduate School of Journalism in New York, Richard Sambrook will tell journalists on Wednesday that even before the Iraq war most US news broadcasters "wrapped themselves in the flag".
Director of the BBC's global news division, Sambrook said the consequence was the US media did not perform the "role the public expects of them - to ask the difficult questions, to press, to verify".
"If a news organisation imbues itself with patriotism, it inhibits itself from asking some of those questions".
He also highlighted the increasing number of journalist deaths over the past year. More than 85 reporters have died over the past 12 months.
Earlier this year, the New York Times acknowledged it had failed to adequately challenge information from Iraqi exiles who were determined to show Saddam Hussein had weapons of mass destruction in a bid to overthrow him.
But the BBC itself has lost a high-stakes battle with Prime Minister Tony Blair's government over its own coverage of the lead-up to the Iraq war.
The publicly funded broadcaster's chairman and director general were forced to resign after a judicial inquiry into the suicide of David Kelly - a weapons expert who was the source for a BBC report that the government "sexed up" evidence of Iraqi weapons of mass destruction.
"We now know that all of us failed to ask the right questions about WMD in advance of the war," Sambrook added.
His speech was in part to announce a new international committee to investigate the dangers facing journalists around the world, under the auspices of the International News Safety Institute.