American drivers tend to be a lot more aggressive and less accommodating of other vehicles on the road and it has gotten much worse over the years. Areas where it was safe to ride 40 years ago or even 20 years ago are now very dangerous for bicyclists. This is by design with the transportation "system" dominated by the motor vehicle and oil industries. Most highways lack a shoulder of any kind and many highways have been turned into freeways.
U.S. city streets have a third of their space dedicated to parking for cars making them more perilous for bicyclists. Schools are forced to pay for buses to bring children to school from kindergarten through high schoo as it is not safe for them to walk or bike to and from their homes. Recently 8 cities had their plans for light rail service killed by people in debt to the auto and oil industries. Unless one has traveled to Europe or Asia they do not realize how different it is in the USA.