Short answer: American traffic engineers put vehicle speed first. European engineers put safety first. The result is 289 deaths per year in LA vs 1 in Oslo.
There's a lot more to it than that. Interesting article
https://www.bloomberg.com/news/features/2022-04-11/-vision-zero-at-a-crossroads-as-u-s-traffic-death-rise
Conversation with an engineer.
https://www.youtube.com/watch?v=P9BUyWVg1xI
I miss Xtranormal. Some of those videos were great.