T O L E D O - O H I O
This is definitely an extreme example but in general Americans are much more laid back than Europeans are. After a long work day Americans would much rather go home, relax and watch some TV than go clubbing and drinking all night. During the day, we drive around in cars instead of walk because are cities are so sprawled out.
I'd also like to point out it depends on WHEN you're there. Most cities in this country with the exceptions of the largest ones, are pretty empty on the weekends, especially Sundays. I've been to all those cities as well and frankly, it's not any different in Tulsa OK, Indianapolis IN, or Louisville KY. However if you're there doing the week between 9-5 you see a lot more people.The reason is mainly the sprawled cities and the malls that comes with it. Instead of walking around Downtown, and eat at restaurants in the city, they take their car to Steak N Shake, McDonald's etc in the suburbs, because thats where everyone lives. As a consequense there are almost nothing to do Downtown and it creates a bad cycle were no one open any shops, restaurants, etc.
As much as I love America it always make me sad when I see how so many cities here are like this. Just visited Cincinnati which is another example. So much potential but totally empty due to the suburban sprawl. Another example is Dayton, OH. 850K metro area but you are lucky if you see one single person walking when you drive around exploring the city. I hope this will change.