The UK driving test is much more stringent than the NY state test (I can't comment on other states - I believe each state defines their own driving test).

The NY test - 10 minutes in the car. I drove around the block; parallel parked, 3 point turn and back to the start. Done.

UK test - an hour in the car; had to drive in urban, country and highway settings (a dual carriageway, not a motorway - learners are not allowed to drive on motorways in the UK); parallel park and answer a lot of questions while doing so.

That's not to discount the fact that the UK has a lot of bad drivers - but the NY test was simply a joke.

If you are considering the safety of the roads themselves, then death/injuries per mile driven is the correct statistic. If you are considering the safety of the society as a whole then it makes sense to consider the obvious advantage of driving less.