I doubt if most people realize how much driving is common in the US. In all but a very small handful of cities, things tend to be _very_ spread out and as a result the number of miles driven is very high. This is the case even in 'urban' environments.
I agree that per mile stats are a far better picture of real risk than per capita stats.
This is a large part of the reason why public transportation doesn't work well in the US.
Public transportation works well if you have a very dense population center that you can saturate with public transportation. New York City is a great example of this with it's subway grid.
It also works well if you have a major work area with an outlying population and can have radial feeds into the downtown areas. Cities that grew up around a single major factory complex or who have a huge amount of downtown business skyscrapers meet this criteria.
but everywhere else, the cost of building public transportation Infrastructure (and then running it) that would be able to get everyone where they need to go with both a decentralized worker pool and a decentralized work area is so high that it is impractical. And as soon as people start needing to have their own care to get to some of the places they need to go routinely, the marginal cost of using that car to go elsewhere is small. As a result it becomes more cost effective to upgrade the road grid than to build enough public transportation to eliminate it.