@Vinz pizza sure, but burgers? There's a possibility that the presence of a fork and knife indicates that the place is a proper restaurant, in which case certain expectations exist that do not exist in fast-food places - which are not considered "restaurants". For example, drinking from a bottle in a restaurant is bad manners but Americans do it all the time. I find that eating a burger with knife and fork is a matter of convenience. I tend to do this in restaurants that provide silverware because their burgers are usually too large. I suppose Americans try harder to eat them with their bare hands, but it seems like more effort for them. I'm not sure about real restaurants that serve burgers in France because I haven't had much experience with those (I'm French but live in California). Also note that traditional French table manners forbid eating anything with hands except for bread, meat with bones, and certain raw or dry things that are more like appetizers or desserts. Burgers are widely understood to be a foreign thing that is super weird to serve on a plate like all sandwiches, so French people would generally not know what to do with it and improvise. Fast-food chain burgers are always eaten with hands with no hesitation.