One minor effect of 9/11 is that the abolition of the  arrangements where US citizens could travel to a number of countries in the US's immediate back yard. I believe the new rules are yet to come into force for the two land borders so that the drunken trips to Mexico for Spring Break can carry on for the time being.

I would agree though with Sven about cultral diversity being more appreciated if you travel. I have qualms whether if, as I am afraid rather too many do, you merely go to a hotel or "resort"  run by an international group you actually get to see any. If the only nationals you get to speak to are the receptionist, waiter and maid you certainly do not get to appreciate the culture.

Far more important than seeing cultural diversity is to appreceiate the common experience of humanity. Without it we too easily dismiss the death of a child in Africa as of little concern as "they are used to it" or concur with the idea that those who do not share our traditions are "other" and sub-human.