Are you being served?

A commentor notes that the proverbial alien visiting Paris and NYC, who I said wouldn't be able to tell equivalent neighborhoods in both cities apart, would find NYers friendlier. I found Parisians to be unfriendly compared to NYers, but didn't know how much of what I sensed came from me being a NYer and thus breaking fewer obvious social rules than I probably did unknowingly in Paris. But still, there was an attitude among people working in shops in Paris that they were really going out of their way to let you into their shop, that you were really bothering them by trying to purchase something. For instance, if I didn't have exact change at a bakery, the cashier would seem more upset about having to go to the register than happy about making a sale. In NYC, when you enter a store or bakery, you're generally asked, sometimes repetitively or by several people, whether anything interests you. Does this mean that Americans are crass and money-obsessed or that French people are rude? Or, to be more charitable, does this mean that Americans are friendly and wonderful or that French people are motivated by non-commercial, more human interests?