A little off-topic, but: I just found out about Comma.ai and... is it really legal in the US? I know it wouldn't be in most (all?) EU countries, as modification

A little off-topic, but: I just found out about Comma.ai and... is it really legal in the US? I know it wouldn't be in most (all?) EU countries, as modifications to the vehicle require certification by a professional engineer. It's kind of terrifying that anyone can modify their vehicle as they please and drive it on the road with everyone else.