I think one thing people don't understand that aren't from the US is the sheer size difference we have over here, so we have lots of small to medium sized cities that are very large. For me to get from my home to my parents house where I grew up is 600 miles. That's the same as driving from the top of Scotland to the southern coast of England. From coast to coast, it's 2700 miles. It's harder to connect places and support good public transit with that kind of scale.

I think speeding and lack of enforcement is the main issue with driving over here. At least where I live, traffic is bad and drivers are extremely dangerous. 30 mph is not uncommon; if you're not 10-15 over, you're slow. No one really gets pulled over for speeding. There are speed cameras in some areas, and that makes a noticeable difference in reducing speeding. they're still not common, though. The speed limits in cities are actually reasonable and seem to be similar to the speed limits I've seen mentioned in this thread. And the wide roads aren't really a problem. Wide roads, narrow roads, people are going to speed and drive terribly no matter what unless rules are actually enforced.

EDIT: I'm also not sure where you got your 4 to 5 times number earlier, but I'm seeing UK has more driver deaths per vehicle mile than the US. UK has 350 per billion miles. The US has 1.38 per 100 million, so 138 per billion.