Some of those big freeway interchanges might be considered bridges. Two or three major freeways could be disabled at one time if a major interchange bombed out of comission. Too awful to contemplate. Traffic is in a permanent stall already.
Golden Gate Bridge, with it's twin towers, would be a likely target. It's the #1 tourist attraction in the USA, highly symbolic for that reason. Suicide bombers could blow themselves up in a truck full of explosives midspan and perhaps bring it down. But I'm sure it's under heavy guard 24/7.
11/2 = "Twin towers - the sequel"?????