US has an extremely different driving culture than Europe. ~13500miles/year for the US; ~8000miles/year for Europe. ~800 cars per 1000 people in the US; ~550-600 per 1000 in Europe.
Also, a larger number of people in the US simply couldn't live life without a car. I'm sitting in my hometown, a mere hour drive away from the largest city in the US, and I'd have to walk 45min to the nearest food. Work would be a 10 mile bike ride each way. This is New Jersey, the most densely populated state in the US.
The seatbelt thing is just us being dumb though.