Bicycles are dangerous in the US because there isn’t a bicycling culture: The bicyclists (that I’ve seen) treat it as a sport, and the cars don’t navigate around them as if the bicyclists are suicidal, which is the safe assumption to make when you come from a bike-heavy European capital.

I can't tell you why honestly. I just know that my near misses have always been with bicycles. For some reason people on bikes think it's acceptable to not slow down when a pedestrian is crossing the street and it's acceptable to just blast past them within a half inch of hitting them.