I was suggesting that undertaking wasn't the cause, as it happens in other countries with lower death rates than the US, eg. Australia.I don't actually think undertaking, passing on the left is a cause, the figures I've seen more recently show US death rates are 4x higher than uk. I don't think you can put it down to our road types limiting speed, our safest roads by far are motorways and dual carriageways, the type of roads you seem to be suggesting are the cause in the US. Our worst type of road is country roads, 2 way, bends with poor visibility, tractors, pedestrians and not always room for 2 cars to pass easily, and that type of road is less common in the US. Maybe, just maybe, our regulations, law enforcement, and culture play a part. And our regulations include the ones we're talking about.
I made no suggestion as to the cause of death rates in the US. I suggested UK death rates may be lower because average speeds here are lower because much of our driving is done in city locations with lower limits and also parking etc. that force people to drive slower, plus our trips are on average likely much shorter, due to living in high density cities.
In the US most trips are done by car, they have little public transport (with some exceptions), and they drive long distances like it is nothing. US average mileage is around double ours. If we had similar do you really think the British superior regulations, law enforcement and culture would prevent us from closing in on their numbers?
Edit: clarified and removed some snark