But even beyond that, most Parisians I met were quite warm and friendly once you got past the initial front, and they loved hearing about living in the USA.
Ok so I have a friend who sometimes tends to oversimplify things. In college (maybe grad school, I forget which story was which) he'd been taking a few years of french, and one course would let him spend a semester in Paris, so he signed up for that.
The main thing he wanted to share, when briefly/concisely relating this little part of his life, was a contrast in dealing with merchants. (We're both in NYC which may be relevant--people here are a bit more terse and rapid than people in the south, the other main area I've lived.)
As he put it, you go into a store here, you want to buy coffee or a red bull or something, you just bring it to the cashier or just say to them "one xyza coffee" or just plop the can on the counter, they say the cost, you pay them and get change, maybe saying "thanks" and you move on.
In paris, as my friend explained it, french culture is different in a very small but very significant (to the parisians) way. You don't just go up to a merchant and buy something with zero ice-breaking. Even if it's minimal, you say good morning (/evening/whatever), how are they,. A very minimal transition--although a longer one is even more appreciated--to demonstrate that you see them as a fellow human, and are interacting with them as fellow people, not as if you're using a vending machine.
Whereas in the US (particularly large cities like NYC), vendors don't really want to talk to you, you don't want to talk to them, you drop some food on their counter and pay them and leave, with no emotional/interpersonal interaction other than the bare-minimum amount you'd give to a vending machine. And, shitty as that sounds, people here generally prefer and even require it.
Humans are made to interact with a tribe/village of a hundred some-odd people (yes, it was bastardized into that monkeysphere meme rubbish, but it has a sound basis in anthropology and social psychology), and if you're going to deal with well over 200 people EVERY DAY, your mind will automatically clench into itself for protection, and start classifying most of your everyday encounters into "other/alien"--the substantive difference is that if your brain sees them as "other", you can shut off the instinct to empathize and try to understand what they're feeling, to feel a connection, to want to avoid having any harm come to them.
If you can think of them as objects (the goal of any wartime propaganda) you can manipulate them without guilt, and treat them as buttons on a screen, not "real people" that will make you care about them simply by seeing that they exist.
So my questions are: did you observe anything like what my friend described, where parisians are offended if you're very blunt/terse with them? And where they're vastly more likely to be cordial and helpful if you greet them and ask (even in a perfunctory way) how they're doing, first, even for corner-store transactions, to signify respect for them as a fellow human?