The chocolate thing is because American chocolate manufacturers use butyric acid to preserve the milk. Basically, using fresh milk in chocolate is expensive, because you need to get it shipped directly and be located near enough to the dairy farm. So they intentionally spoil the milk in a controlled manner. This allows them to preserve the milk (as opposed to having it spoil naturally and go completely rancid,) which allows them a much more relaxed manufacturing process. This controlled spoiling method produces butyric acid in the milk.

The issue is that butyric acid tastes like vomit. Americans are used to the sour taste and don’t even really recognize that it’s not what chocolate is supposed to taste like. To them, that sour note is just part of chocolate. But Europeans come to America (and are used to fresh milk in their chocolate), and they are horribly disgusted when they taste American chocolate for the first time. Because Europeans aren’t used to having that sour note in their chocolate.

This is also why so many Americans fawn over foreign chocolate. It is seen as more luxurious, but most Americans can’t really place why it tastes so much better. The reason is the lack of butyric acid.