Note that the places Al Queda has discussed attacking in the US are places where few permitted concealed handguns are allowed

From Yahoo News:

Al Qaeda militants in Syria are plotting attacks to inflict mass casualties in the West, possibly against transport systems or "iconic targets", the head of Britain's MI5 Security Service said on Thursday.Speaking after gunmen killed 12 people in an assault on a French satirical newspaper, MI5 boss Andrew Parker warned a strike on the United Kingdom was highly likely. . . .

From the Daily Beast:

In the Spring 2014 issue, for example, Inspire proposed attacking cities and military facilities in northern Virginia, the site of the U.S. Open tennis tournament, and targets in Los Angeles and Chicago. . . .

 In Los Angeles, there are only about 240 concealed handgun permits in an adult population of about 8 million people.  In Chicago, it costs about $500 to go through the process of getting a concealed handgun permit.