Usually those indexes are not as diversified as the US index is. Take German DAX for example. It's mostly made up by chemical, car and industrial companies. The

Usually those indexes are not as diversified as the US index is. Take German DAX for example. It's mostly made up by chemical, car and industrial companies. The post-war German economy did really great as well, but many leading German companies are private. Furthermore, the USA is one of the biggest economies in the world, way bigger than most single countries on their own.