Interesting that you consider US highways and streets to be well designed, given that they are objectively substantially more lethal to their users than European roads.
a) training and education - it is way more difficult and takes longer to get a driver's licence in Western Europe than in the US
b) mandatory vehicle inspections - I think this varies by state in the US, but even the strictest state legislation is still less strict than Western European countries when it comes to allowing dangerous vehicles on the roads
c) less regulation for truck drivers' work hours - I think in the past decade, sleep deprivation amongst transportation workers and the results thereof has received increasing exposure in the press, which is good, but awareness only goes so far
I think attributing that to the design of the roads is kinda silly. We have very low standards when it comes to acquiring a license to operate a vehicle.
I think attributing it to any one cause is kind of silly. It's a fact that American cities are much more car centric with higher speeds and fewer areas with traffic calming measures, all of which make the roads much safer.
Daily highway driving is much more common for commutes and errands, suburbs have dangerous arterial street designs.
I'm sure there's more to it, such as licensing and vehicle safety measures, but American highway design (and making local roads into mini highways) is a part of it.
Also the EU measure is EU-wide, and not all countries in the EU are as strict as say Germany for licensing.
a) training and education - it is way more difficult and takes longer to get a driver's licence in Western Europe than in the US
b) mandatory vehicle inspections - I think this varies by state in the US, but even the strictest state legislation is still less strict than Western European countries when it comes to allowing dangerous vehicles on the roads
c) less regulation for truck drivers' work hours - I think in the past decade, sleep deprivation amongst transportation workers and the results thereof has received increasing exposure in the press, which is good, but awareness only goes so far