They are if you look beyond the color of skin. And there's a big difference between Japan and Haiti. Compare the economies of Japan and Haiti and get back to me.
1: the condition of having or being composed of differing elements : variety; especially : the inclusion of different types of people (as people of different races or cultures) in a group or organization
2: an instance of being composed of differing elements or qualities : an instance of being diverse
By the dictionary definition, as opposed to the PC definition, Japan is perhaps the least diverse country on the planet.
Haiti may not be far behind. While it was settled by people from all over West Africa, they've melded into a common way of life. They are divided into gangs that fight each other,but the divisions aren't really ethnic in nature. More like the Crips and the Bloods.