Lifestyle's part of it, but the US is bigger than any European country, unless you count Russia as European. Our states are about the size of countries there, and out west, some counties are bigger than eastern states. It's not like driving from London to Oxford. Outside of metro areas, you have to go a long ways to go anywhere. At 70 mph, I'm 5 hours from Detroit, 8 hours from Chicago. It takes gas to get places, and at least in the northern states, you need vehicles that can handle lots of snow, which usually means 4 wheel drive, which usually means SUVs.
I know the US could do better in a lot of areas here, but you can't compare apples to oranges.