Try this one :
http://www.executiveplanet.com/index...=United_States
They have a load of info on most of the various countries and cultures in the world. If you're interested in others, just go back to their home page from that link and you'll find the list. In the past however I've found some of the links don't work. But if you just type in the country that interests you in place of United States in the link above, you'll usually get there.
If you're interested in teaching cross cultural differences like this, one fun way is with a quiz, which you can then follow up with a reading text explaining the reasons for the answers. You'll find both a quiz and an article which could be adapted on my site
here - but it's general, not specifically US oriented. You could work up something similar though with the info from Executive Planet in the link above.