Why There Haven't Been More Bombings Here

From the explosives in Umar Abdulmutallab's pants to Faisal Shahzad's smoldering SUV in Times Square, most recent terror attempts in the US have failed spectacularly. Militant groups who regularly and successfully carry out bombings in Afghanistan and Iraq have a much tougher time launching attacks in the US. Dina Temple-Raston explains why on NPR:

• The Internet can't actually teach you how to make a bomb any more than "watching a couple of Major League baseball games on TV will provide everything needed to step up to the plate and connect with a fastball," writes Temple-Raston. Even the Harvard-educated math genius Ted Kaczynski spent years studying chemistry and testing his bombs.
• Bomb materials are much harder to get in the US than in Afghanistan. The fertilizer in Shahzad's SUV, for example, was the wrong kind, because the kind that blows up has been regulated since the 1995 Oklahoma City bombing.
• Successful bombings usually require teams of people who know what they're doing—financiers, explosive experts, location scouts—but most stateside terrorists have to work alone.
• Even if you manage to build a bomb, you need to test it—and it's pretty hard to avoid being noticed testing bombs.

(More terrorism stories.)