Originally Posted by menton1

Wearing jeans and sneakers in France especially while dining, is like broadcasting a message to the locals: I'M AMERICAN AND I DON'T CARE ABOUT WHAT'S ACCEPTABLE HERE.

It's respectful to try to immerse a little bit in the place you are visiting that has a different culture than your own. Leave the jeans & sneakers home. Try also to speak in a lower voice in public than you do in the US. (And Americans wonder why the French get non-plussed at their attitude)