Dispite Grinner's claim to expertise on the US, I find that a country and population this big and diverse is hard to pin down and describe. I do know that a lot of people never end up leaving the US, or travel overseas only a few times in their lives, whether because of finances, the opportunity to see and experience many things in the US, or, as has been suggested, from lack of interest. Then we have the people who sojourn annually back to the homeland--include millions of Latin Americans (many of whom don't need passports to do so).
As far as the ignorance of the US populace as to the rest of the world, I note in my travels around Europe that many of the people I end up talking to--sales clerks, bar tenders, cabbies, and the like, don't know squat about the US either--even those with a cousin in Chicago or some relative in North Carolina.
Although geography was one of my major areas of study in college, I know many people detested the subject. For many Americans, in would seem, learning about the US is geography enough. Let's face it, this is a country with 50 states (plus DC), around 293 million people (excluding several million unaccounted for and in the country illegally), and 3,717,792 square miles of territory. Europe is somewhere between 3,800,000 and 4,057,000 square miles, depending on how much of Russia you want to include. UEFA recognizes around 53 entities as European nations--including Israel and Kazakhstan, which is pushing it a bit. Consider also that such places as Andorra, Liechtenstein, San Morino, Malta, the Faroe Islands, Luxembourg, and, possibly, the Vatican are viewed as "nations" when they'd not qualify as states over here.
From a geographical and, in some respects, cultural standpoint, learning about this place is about the same as learning about Europe. And travelling through the US can be as rewarding and time-consuming as travelling through Europe. As I mentioned before, we have a lot of ethnic groups, regional differences, and differing climates, so a lot of people probably don't see the need to spend the extra cash and inconvenience to bolster someone else's economy. Seriously--why go to the beach in Spain when Hawaii beckons, why fly to the Alps when you can drive to Vail?
People tend to learn what they need to know. Those who don't need to travel overseas probably don't feel the need to learn about the places never seen.
By the same token, even on a site like the Red Cafe I see that a lot of the posters who view themselves as learned, wise, and worldly view the US through eyes no more sophisticated and accurate than those of the "red necks" they so eagerly condemn.