Transit changes are not required to implement the safety changes made by other countries. The cause and effect is reversed here: safety changes make transit more appealing because safety changes tend to decrease peak vehicle capacity, but transit does not make safety more appealing to untrained and overconfident (or willfully unsafe) drivers. You can’t just focus on transit while ignoring drivers and expect people to stop dying.
I remember during the first days of Covid lockdown how 99% of the cars on the busy hill outside my apartment were replaced by transit, with a commute distance of zero miles. The people who liked to do downhill racing on that hill during the day sped up from their usual brake-screech limits of 40mph to as high as 70mph, in a 35mph residential with an unsignaled busy crosswalk. And they continued doing this until the end of the lockdown when other cars got in their way again. Transit might reduce total car volume but it would increase the mean kill rate per roadway vehicle without safety culture and spending shifts.