Why does the public let go unchallenged the claim that there will be a "next 9/11" to prevent?
The 9/11 attacks were the most ambitious terrorist attacks in history. They certainly terrorized the United States, and government officials obviously remain terrorized to this day. So in that sense, they were kind of a success. They also had massive blowback that Al Quaeda might not be keen to repeat.
Before 9/11, bin Laden was a folk hero in some parts of the Muslim world because he fought the Soviet occupation of Afghanistan. After the atrocity he masterminded, most of his financiers and sympathizers dropped him like he was radioactive. Middle Eastern governments that had formerly turned a blind eye to Al Quaeda started shutting down its finance network and jailing its contributors, raiding training camps and arresting radical clerics. Then there is the US armed response, which was deeply misguided in important ways but which undeniably brought ruin on Al Queada and the Taliban government of Afghanistan. Since at least the battle of Tora Bora, Al Quaeda has been struggling to survive. It's hard to see how redoubling American resolve, just now when the public is war-weary, cynical, and worried about the war debt, would advance the aim of a global Caliphate.
It has also been said that the 9/11 attacks were self defeating in the sense that exactly because they were so devastating and well-planned, they are nigh impossible to surpass. Next to them, just bombing an embassy looks like small time. So the effectiveness of typical terror attacks may actually have been diminished because the public's expectations have been raised.
So, even if any organization could pull off "another 9/11", I seriously question whether they would want to. I believe the radicals' current objective is to get the US out of Afghanistan so they can rebuild their safe haven there. In other words, to pick up the pieces from the blowback from 9/11 and get back to where they were on Sept. 10, 2001. There is considerable doubt whether this is possible: the US will definitely pull out, but its drones will still rain Hellfire missiles from the sky day or night, and the US-backed Afghan army is in a position to keep the pressure on for a good long while.
Which brings me back to why preventing the "next 9/11" is something we should be worried about. If bin Laden had 9/11 to do over again, knowing the consequences for his organization and his agenda, would he go for it? I have to go with "no." Why can't any politician stand up and say that? Claim some credit for the progress in the "war on terror" instead of jumping at shadows?
Of course, I can answer my own question. The bogeyman of terrorism serves the authoritarian purposes of the government, so they refuse to abandon it. But please, let's start calling them on it.