Right, George, the conclusion was mine, as it's my personal experience.
But, when you see how people get angry over some small stuff on this forum, one wonders..
I was thinking it's probably something in the processed food..
But I'll welcome comments...
Frankly I doubt that urban Americans eat significantly more "processed" food than do their French counterparts. That of course depends on your definition of "processed".
I was once angrily chewed out by a very cranky Parisian shopkeeper when I had the temerity to walk into his shop - through an unlocked door, with no warning sign - during his self-appointed lunch hour. I laughed & apologized, then rolled my eyes as he persisted. That made him more enraged, so after a brief universal hand gesture I left, listening to his references to "salles Americans" as I exited. I don't think that was at all typical - in my experience people everywhere - Frenchmen included - tend to respond in kind to what you show them.
Americans are a more diverse lot than most other people. To a greater degree than other countries, one is an American by choice, and not necessarily by common tribal, linguistic, or cultural traits. I suspect that is likely the source of most observable differences between us and others. (Where I grew up if you answered the question "What are you?" with "American", you had to be fairly tough. The common answers were "Irish" (preferred) , or "German", or"Jewish" or "Polish", or "Italian", or "Syrian" . ) In most cases the Jewish, Polish, Italian, & Syrian kids parents spoke their native language at home (the Germans were by then quite assimilated). Today the actors have changed a bit, but the basic facts remain the same. There is some of this in Europe as well - but not nearly to the same degree.
With respect to expressions of anger on these fora - I do agree with you that they seem odd and out of place. I don't understand the point or meaning of anger with one whom you haven't met, don't see, and communicate with only through the typed word and generally on non personal subjects.
I've never joined such a forum in another country, so I don't know if they are different. I note that some of the Canadians here can get a bit angry and hyper critical (but then there are easy-going, tolerant, lovable folks like Mame among them) and Nimh (as you may recall), could get a bit angry. I just don't know if Americans are different in this aspect of things. I am skeptical, as you can detect.