Exactly Maya, I think we're talking about Americans who care about fashion and style. Lord knows what to say about the croc crowd. But even stylish Americans are influenced by the larger American culture who sees it as frivolous, pretentious or not worth the effort. It's like we have to extra friendly or slightly apologetic about dressing well.
Even many stylish Americans seem insecure about individual style and eager to please. Many jump on trends because we're afraid to look out of touch. That's why we look to the Tim Gunns of the world to teach us "taste" (preferably with a reassuring exotic accent). How many of us have the confidence to wear something that no one else here approves of?
So I don't know if it's that Americans don't pay enough attention so much as we're overly eager. Have you noticed how few women on the street are wearing straight leg jeans? It went right from bootcut to skinnies! Even crocs or uggs are an example of that, millions of people didn't have the self confidence to decide the trend wasn't right for them.
Stylish French women just seem more confident and laid back. They're a little more subtle and less "done up". They know their style and stick to it. More women seem to stick to classics or work in trends according to their individual style. They buy less, but they buy better.
These are broad generalizations of course. I've never been to Paris and I hate to jump on the "Ugly American" bandwagon. I'm sure there are plenty of confident stylish Americans and poorly dressed French women. I think there are lessons here though and I'd like to incorporate them into my style.