A convenient threat?

According to the nation’s lawmakers, the United States is now facing the greatest peril since the 9/11 attacks, prompting weeklong closures of 19 diplomatic facilities in the Arabian Peninsula and Africa, evacuations in Yemen, and a worldwide travel alert.

"[This is] one of the most specific and credible threats I've seen, perhaps since 9/11," House Homeland Security Chairman Mike McCaul, R-Texas, said Sunday on CBS News' "Face the Nation."

The embassy lockdowns are indeed extraordinary: Former US Ambassador to Iraq Christopher Hill told CNN that he had never seen anything like it.

“I think this, closing all of these embassies in the Middle East to North Africa is in fact unprecedented. At least, I didn't see this during my career," he said.

The concern over a possible threat to American facilities and personnel is so severe that it has all but silenced criticism of the US National Security Agency's vast secret surveillance programs, which had been gathering steam in recent weeks.

Europe has been furious with Washington ever since ex-intelligence analyst Edward Snowden made scandalous revelations about the US government’s all-encompassing data sweeps, which included spying on America's partners during conferences in London in 2009.

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Some members of Congress have threatened to curb the NSA’s enthusiasm. A proposed amendment to the Defense Department spending bill that would have imposed limits on surveillance was narrowly defeated last month.

The American public, too, had been growing restive in the face of ever more damning revelations, such as last week’s bombshell on the XKeyscore program, which the NSA itself trumpets as its "widest-reaching" system for culling intelligence from the internet.

For the first time since the Sept. 11, 2001 attacks, more Americans — 55 percent — were concerned that government surveillance programs would go too far in trying to protect them against terrorism, versus 36 percent who say the government isn't doing enough, according to an NBC/Wall Street Journal poll released last week.

Then, a threat of such overwhelming proportions emerged that few would dare to suggest that America now needs less protection, rather than more, and the NSA was the hero of the hour.

An intercepted electronic communication between Al Qaeda’s two top leaders indicated that they wanted to “do something big” to mark a major Muslim holy day.

Ayman al-Zawahiri, who took Osama bin Laden’s spot as head of Al Qaeda, and Nasser al-Wahishi, leader of Al Qaeda in the Arabian Peninsula, wanted to mark Laylat al-Qadr, when Muslims celebrate the day the Quran was revealed to Muhammad, NBC News reported. This year it fell on the weekend of Aug. 3 and 4.

No details about any specific type of attack or a particular target were mentioned, according to law enforcement and intelligence sources.

Officials do seem fairly confident that they know where the threat is emanating from, however. The State Department has ordered the evacuation of all non-essential personnel from its embassy in Yemen and has urged all American citizens to leave the country.

The British have already evacuated their embassy in the Yemeni capital, Sanaa.

These actions, along with the heated rhetoric accompanying the measures, has raised the temperature at home.

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In the face of such danger to the homeland, says William Martel, associate professor of international security studies at Tufts University’s Fletcher School, Americans are willing to do whatever it takes.

“[If it is true that] Al Qaeda has regrouped and is a global threat again, that … will drown out debate about the NSA right now,” he told GlobalPost. “It will overwhelm all other concerns. It is such a powerful tendency and instinct in the American public to focus on the threat, and sort the rest out later.”

This is certainly true in the halls of power. President Barack Obama's enjoying a rare moment of approbation from even his harshest critics.

Rep. Peter King, R-NY, is not known for praising the administration, but he applauded the government's decision to close its diplomatic missions.

"I give them credit," he told CNN’s Wolf Blitzer. "I think the government is doing exactly the right thing here."

King said the threat was the most specific he had seen in a decade.

“[There is] very specific information about the fact that there is a plot, that attacks are planned, but, again, it is not certain as to where.”

A weeklong closure of multiple installations and a monthlong worldwide travel alert may suggest the very opposite of specificity, as does a vague reference to “something big.” Some observers are a bit skeptical.

“We might be forgiven for the thought that the embassy closures provoked by terrorist threats were all very convenient,” wrote British journalist Richard Norton-Taylor, who writes for the UK’s Guardian newspaper on security matters. “For far too long the intelligence agencies of the US — and Britain — have been allowed to hide behind a wall of secrecy as they hoisted the flag of "national security" before which everyone else must genuflect.”

But that kind of sentiment is unlikely to gain much traction right now on this side of the pond.

Sen. Saxby Chambliss of Georgia, the top Republican on the Senate Intelligence Committee, was quick to give the NSA credit for uncovering the plot.

Those programs "allow us to have the ability to gather this chatter," Chambliss told NBC’s “Meet the Press” on Sunday. "If we did not have these programs then we simply wouldn't be able to listen in on the bad guys."

This kind of thinking can backfire, according to Representative Adam Schiff, a Democrat from California.

“I do think that in this context, as in others, people have commingled several different NSA programs to try to defend, in particular, the bulk metadata program,” he told MSNBC Monday morning.

There's no evidence that the most controversial of the NSA programs, known as PRISM, contributed to uncovering the present danger, he added.

“I don't think — although people have been a little sloppy in talking about this plot — that there's any indication that that metadata program played a role,” Schiff said. “It would be very unusual for a bulk collection of domestic calls to be telling us about an AQAP plot against foreign embassies and consulates.”

Whatever is going on, there's little to be done about it now, Tufts University’s Martel says. In the post-9/11 world, it's simply too dangerous out there to take chances.

“We have learned as a society that it is better to err on the side of caution,” he said. “We cannot be dismissive or cavalier about the threat.”

He doesn't think the threat has been hyped for public relations purposes, although he does not totally discount the prospect. But if that is what's going on, he warned, the costs will be steep.

“If the threat is being inflated it will become clear later on and there will be a political price to pay for that,” he said. “If people are playing at some funny business it will come out … and there will be a political backlash.”