Well, most of the freeways or interstates are only 2 lanes and lane discipline is fairly reasonable but as you say around the cities where the number of lanes increase its so dangerous and the more lanes the more dangerous. Having driven through Denver in the rush hour, which lasts from about 6 in the morning to Ten at night you need to know exactly where your turn off is, in fact its best to just stay in lane 2. As for it being safer, I couldn't say for sure but the death rate on Motorway type U.S roads is astronomical compared to The U.K, but this could be due to other factors. For example in Colorado no need for bikers to wear crash helmets and the police can't stop you for not wearing a seatbelt, even though its the law to wear one Also many, many deaths on Freeways/Interstates are caused by drivers falling asleep
Pete