I disagree. You're sharing the road with vehicles 10x heavier than you. People have heart attacks, go into diabetic shock, blow their tires, etc. Sure, those things don't happen often. But if they do and you're in the way, you'll have brain damage at best. There's not only other drivers to be wary of, simple road hazards that are nothing to a car can cause great harm. Sewer grates, random debris, pot holes, pot holes hidden by puddles, oil slicks after a rainfall, people pulling over to the side of the road without looking because of a siren etc. At times, even the wind becomes a dangerous element.

You mention walking should be fairly effortless. However, I've seen so many near misses because people walking are so buried in their phones that they almost get hit. Also I find that people put too much trust in traffic lights instead of simply looking both ways before crossing a street.

Cycling in large American cities built for automotive traffic is, unfortunately, not for everyone, not yet.

You have to reach the point where vigilance doesn't cause anxiety.