On a site dedicated to geopolitics a chart like this can not be lacking. For extra interactive data go the Guardian to see the original map. Note that although Japan has a national debt of 200% GDP, it still is categorized as ‘high grade’ because it has a highly competitive economy. This cannot be said of the US but is even rated prime anyway because it own’s the world reserve currency, a left over of WW2. This way the US can export its inflation to the rest of the world.