I agree the NHTSA is way too slow, but damn am I glad they're doing the work! I love that they're checking everything carefully and doing the research before approving new designs.
They are not doing their work, their work is to allow highest available safety standards to be implemented, not to block progress. Their inability to allow curved rear mirrors killed god knows how many US people. You have decades of statistics form ie Europe to back it up, same as for this topic (OK decade and a half for lights).
I suspect its rather a typical lazy government bureaucratic hell case.
The NHTSA is regulating all the wrong things. How many people have been killed by wrong headlight shape? How would you even test that regulation? Meanwhile, people are free to go 100mph in cities, with the trivially demonstrable deaths that causes for no upside.
They could regulate cars to make sure they're incapable of going faster than a certain speed, but people seem to want faster and faster cars for some reason and I'm guessing most accidents aren't happening at > 100mph speeds
