It's the urban planning, but I'll point out that it's the requirements and responibilities put on the drivers as well. Driving lessons for me consisted for 80% of learning how to ALWAYS ALWAYS track all the cyclists and pedestrians in urban environments, how to approach an intersection and have complete visual on whatever the weaker parties might be doing. A very defensive "assume weird shit can happen any time, and…
It also helps that "the car driver is to blame until proven otherwise" is the actual law in the Netherlands, which is motivated precisely because of that power dynamic. Essentially, the responsibility defaults the more dangerous vehicle. (for some reason this always is controversial with a lot of Americans whenever it is brought up in on-line discussions)
Because a car is essential for economic survival in the USA, it's probably difficult for some to accept alternate realities from the status quo.