If you live in Jamaica, you have to leave Jamaica to have a change of scenery. You pretty much need to leave Jamaica to experience anything remotely different climate, scenery, culturally.. People dont want to spend their entire life on an island seeing the same shyt every day.
An American can get in their car and go to snowy mountains for skiing, they can go to sub-tropical environments for beaches, they can go to frozen lakes to fish, they can go to the desert, they can go to giant woodland forests, they can go to open plains. Damn near anything you want to experience scenery wise you can experience in America using a car. The American southwest is completely different from the Northeast, midwest, northwest, south, etc...
Also remember an American DID NOT NEED A PASSPORT to visit Canada, Mexico, Jamaica, Bahamas, etc...until 2009!
I went to the Bahamas when i was 16 and we didnt need a passport. So not having a passport is not evidence that Americans didnt travel.