When I think of all the dialects and local accents there are in the U.S., I know that this movie is universal in its message: once you cut through the differences in communication, people are people and the same everywhere. Some better than others. In this film, the small-town people are very good.
The theme is similar to that of the television series, 'Northern Exposure.' Someone arrives with preconceived notions about a less-sophisticated burg and has his opinions turned around. People eat strange food, not found elsewhere (I'm thinking of my relatives' 'hog maw'!) and have a funny way of expressing themselves (I'm thinking rural Maine - Marshall Dodge style).
Even a novice French speaker such as I could understand most of what was said as part of the comedy. For the less brave, English subtitles are the best guide.
The humor is never over the top. There are no sex scenes, the swearing is of the local type, and the themes are universal - overbearing in-laws, career goals, managerial challenges, and leaving home(s). I can see why this movie was so popular in France.