I don't believe Americans are fake, but I do believe that Americans are trained since an early age to display at all times that they're not a threat, and that is kind of sad.
More contemporarily, I can speak specifically to black culture- if you're black interacting with white strangers in a foreign environment, you may find yourself being overtly friendly to strangers simply as a means to compensate against any potential stereotypes. I'm sure being a minority in any situation can elicit this reaction though, including being a white minority. And I've also experience d the opposite, where I'm a "white" minority- and I had to simultaneously present myself as not being a threat, but also not an easy victim.
Interesting. Since I'm the fish who can't see the water, could you provide me with some examples of this?
When I was younger and would go hiking or climbing in Scotland and Wales, I would definitely have to be quite mindful of "showing I was not a threat" when entering small village stores and pubs there.
The more densely and contiguously populated and area is, the easier it is to (a) feel a part of the "in group" (b) not feel aware of the difference between "insiders" and "outsiders".
My experience is that the behavior you describe in Americans is roughly proportional to population density and tourism levels. Areas with lots of people and/or lots of visitors do not require this "low threat establishment". Areas with less people and/or less visitors often do so. I think this is true of Europe just as much as the USA, and I would guess it is probably the same worldwide.