I think he means suburban mass transit or smaller cities. However unlike Israel our attackers (Arabs) will stand out outside of major urban immigrant cities. Attack a red state small city or suburban area, and watch a local mosque burn to the ground. I think one of the reasons why the muzzies have not attack in the US is because the political fallout would be negative to their cause. GWB poll numbers are below 50 percent and support for the Iraqi war has fallen. An attack now would boost US support for GWB and his policies in Iraq. Personally I would leave the US alone and let the Democrats undermind the US will to fight.
These guys aren't the brightests bulbs. The same situation existsed in Britain, and they attacked there. Of course, we have yet to see if the attacks steeled the nerves of the Brits, or has had the "Madrid Effect" on them.
I'm not convinced that the next attack in the US will be perpetrated by Arabs or anyone appearing middle-eastern.
That would be smart but I think it just goes against their nature to not be out killing infidels.