I used to travel. Africa, Australia, Japan, Europe, Mexico, etc.
His point about Americans not traveling is valid. I wonder if part of the reason is that North America is so far away from everywhere else. It takes 11 hours to fly from Berlin to Thailand, but it takes 25 hours to fly from NYC to Thailand. Most Americans probably have to get to NYC or LA to get anywhere else in the world, which can be another 3-5 hours of flight time. The long distance is the main reason I don't travel as much as I once did.
However, in Mexico, the default foreigners are usually from the US.
Canadians travel, so you can't excuse the distance.
I think the problem is (I say this as a Canadian) that the US has a very insular streak to it's fabric that is manifested in ways such as this. This same streak that caused the US to join both world wars when they were half over.
My guess is that it stems from the individual nature of the founders, along with the split from England. This isn't as strong in Canada and Australia because those countries remained extensions of the Empire and thus were automatically and continuously connected to the larger world.
The US spent a better part of the 1800's focusing exclusively on North America.
Another alternative hypothesis for you to consider: there is already so much beauty, novelty, and interesting diversity in the US that it takes a slightly bigger push to get past this local maxima. No offense, but if you chopped out and stitched together all of the interesting bits of Canada you would have a land mass that was about the size of California and with a similar population; in the US we have 49 other states to tool around in as well that present a much greater diversity in terms of environment and inhabitants. We get all that without needing to use a passport, exchange currency, or try to learn to speak like a tourist in another language. It is not the same thing as real international travel, but it is a close-enough approximation for some people that it serves as a reasonable substitute.
there is already so much beauty, novelty, and interesting diversity in the US that it takes a slightly bigger push to get past this local maxima
That statement though is illustrative of my point, though. Canadians and/or Australians will either view their country as boring or too large, and so they head overseas. Americans don't.
I don't think this speaks so much to the actual fact than it does to the way one looks at the situation.
Another aspect is that I don't have to travel to the other side of the world to learn about other cultures, necessarily; I just start talking to my neighbors or coworkers. Is it the same? No, but it's not worthless and you can get up close and fairly personal. I won't learn enough to blend in with that culture by any means but that takes months anyhow.
Central (in particular) and South America (to a lesser extent) have way more American travelers than anywhere except Europe (at least this has been my anecdotal experience with nearly a year in Mexico/Central America). Costa Rica is practically the 51st state and south Nicaragua is well known for it's cheap land and American surfer ex-pats. Of course, flights to CA are super cheap from the US and this probably explains it.
The other thing that I've noticed is that Americans from the West Coast are much more likely to travel (of course, I'm from the west coast so this might be some confirmation bias).
(opinions based on a little more than two years or so of ongoing travel and probably something like 30 countries)
It might be that west coast goes to south/central America more often and ease coast goes to Europe, becuase I know a lot of people who have gone to Europe from here but few that have gone south. It makes sense, if I have a week off getting to Europe is only 5 or 6 hours each way, which is roughly the same as california. Flight time is not the big time suck though, it is waiting in airports for connections. A direct flight to central Europe is a lot shorter than a hop from NYC to LA or TX and then a connection to a flight going to south America.
I feel like you're making the excuse. You don't have to go to Thailand, there's plenty of different cultures/destinations near the US (Europe, Southern Americas and possibly even Japan). Instead of comparing Berlin to Thailand with NYC to Thailand, try NYC to Berlin.
This is coming from someone living in Perth, who has to travel forever to get anywhere, including having to go through Sydney or Singapore to get anywhere distant.
However, in Mexico, the default foreigners are usually from the US.