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