Apparently, the threat is both serious and specific.
The United States ordered 22 diplomatic missions closed and issued a worldwide travel alert for U.S. citizens.
The threat comes from Al-Qaida in the Arabian Peninsula, AQAP, the most lethal branch of the terrorist organization.
"After Benghazi," said Sen. Lindsey Graham, R-S.C., "these al-Qaida types are really on steroids thinking we're weaker and they're stronger. ...
"They want to drive the West out of the Mideast and take over these Muslim countries and create an al-Qaida-type religious entity ... and if we ever take the bait and try to come home and create fortress America, there will be another 9/11."
By the time this column appears, America may have been hit. Yet is it not time to put al-Qaida in perspective and consider whether our Mideast policy is creating more terrorists than we are killing?
In 2010 America lost 15 citizens to terrorism. Thirteen of them died in Afghanistan. The worst attack was the killing of six Americans at a Christian medical mission in Badakhshan Province.
Yet, in 2010, not one death here in America resulted from terrorism.
That year, however, 780,000 Americas died of heart disease, 575,000 of cancer, 138,000 from respiratory diseases, 120,000 in accidents (35,000 in auto accidents), 69,000 from diabetes, 40,000 in drug-induced deaths, 38,000 by suicide, 32,000 by liver disease, 25,000 in alcohol-induced deaths, 16,000 by homicide and 8,000 from HIV/AIDS.
Is terrorism the killer we should fear most and invest the lion's share of our resources fighting?
Since 9/11, al-Qaida has not proven a terribly effective enemy. Some plots -- the shoe-bomber on the airliner over Detroit, the Times Square bomber -- failed from sheer incompetence. Other attacks have been thwarted by excellent U.S. intelligence and counterterrorism work.
Our home front has been well protected.
But by having fought a "war on terror" overseas in Graham's way -- invading, occupying, nation-building in Afghanistan and Iraq -- we lost 6,000 soldiers and brought back 40,000 wounded Americans.
Were the wars in which we suffered such casualties, and that cost us $2 trillion and counting, really worth it? Did they make us more secure?
The Taliban are making a comeback. Iraq is sinking into civil, sectarian and tribal war. Our influence in the Islamic world is at a nadir. And Graham concedes the enemy that we went over there to destroy, al-Qaida, is not only in Afghanistan and Pakistan, but Yemen, Iraq, Syria, Libya and Mali, and is now "on steroids."
Ten years ago, anti-interventionists warned that a plunge into the Islamic world would produce what it was designed to prevent. We could create more terrorists than we would kill.
For the root of 9/11 was Islamic hatred of America's perceived domination and a fanatic determination to drive us out of their world.
They were over here because we were over there. And if we went over there in even greater force, even more Muslims would rise up to expel us from what is, after all, their neighborhood, not ours.
So the anti-interventionists argued.
Dismissing such warnings as "isolationism," George W. Bush launched the war. The result? Precisely what opponents of the war had predicted, an al-Qaida that has metastasized and is now "on steroids."
Now, Graham says, al-Qaida wants "to drive the West out of the Middle East" -- their objective all along -- and "take over these Muslim countries and create an al-Qaida-type religious entity."
But was it not the United States that dumped over Moammar Gadhafi and opened the door to the al-Qaida that perpetrated the Benghazi atrocity?
Was not liberating Benghazi why we went to war?
We liberated it, but for whom?
Gadhafi, though himself a terrorist responsible for the Lockerbie Pan-Am bombing, was an enemy of al-Qaida. So, too, are Hezbollah, Iran and Syrian President Bashar Assad. All are fighting to prevent a takeover of Syria by rebels whose principal fighting force is the Nusra Front, an affiliate of al-Qaida.
Does not Vladimir Putin have a point when he asks why America is arming an insurgency dominated by the sort of people who did 9/11?
Graham says al-Qaida wants to take over "Muslim countries and create an al-Qaida-type religious entity."
Yet the Muslim country al-Qaida has the best chance of taking over is Syria. And we are arming the rebels who are allied with al-Qaida and who want to take over Syria?
"If we ever take the bait and try to come home and create fortress America, there'll be another 9/11," warns Graham.
Graham is saying we must stay in the Middle East and fight on until al-Qaida, which has grown since our intervention and because of our intervention, is annihilated.
Otherwise they create a caliphate and come over here and kill us all.
After 58,000 dead we left Vietnam. How many Americans have the Vietnamese killed since we left?