The issue is that international travel is only for rich people here. Most of us struggle to pay rent and buy groceries, we can't spend thousands of dollars on a vacation (and most jobs don't give vacation time). It isn't a quick easy trip on a train for us, it's passports and plane rides, ykwim? I have never really gone on a real vacation, ever, because that is for rich people. When I was a kid I did go on a few trips to see family, and as an adult to a couple of weddings, and that is the extent of my travels. The only other country I've been to was Canada for a family reunion and that was before that required a passport (now it does).
Traveling around the US is like traveling around the EU; how often do Europeans get on a plane and go to Africa or Asia? Now factor that that number will still be higher because vacation time from jobs is normal there. A lot of us have none, a lot have two weeks tops. And you get in trouble for using it at many places.