My wife grew up in England and uses a knife and fork to eat pizza. Her father made a trip to the U.S. one time, and went out west with her and her first husband. In a restaurant in some western city, they stopped to have a meal. Her father had never eaten a hamburger before, so he ordered one. He ate it with a knife and fork. My wife said the looks on the faces of the people at nearby tables were priceless. But since he was foreigner, I guess he could be excused.
A family friend married to a Dutch man was entertaining guests from the Netherlands and served hamburgers. She was not pleases when they all called her a barbarian for eating the hamburger with her hand.