Well there is reason really. Look at the US on the map then look at Sweden.

There are 3,974,100 miles of road in the US. Thats a lot of road to keep in top notch shape with government money. Where as Sweden has 263,030 miles of road plus you guys produce a lot of tax money.

As to width wise, well there are simply A LOT more cars in the US than in most other countries. Not to mention most cities here suffer from suburban sprawl, where each home has at least two cars that they use to go everywhere all the time. Also most cities other than the very largest(NYC, Chicago, LA, Boston, Seattle, San Diego) do not have a effective established mass transit(light rail, subway, streetcar, etc...) system that most of Europe has.