US auto regulations are extremely conservative on the lights/signals front, have been for a long time. Some European car designs in the late 20th century were compromised when brought to the US because the headlights had to be made worse (in an aesthetic sense) even though there was no safety reason to do so — Citroen DS was one of these.

And maybe they should be conservative, but I don’t see how anyone can argue that it should take a decade to get something like this approved (or formally rejected).