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.
It means we are an immigrant nation, Japan is not. Neither is China, nor Korea, nor Vietnam.
While we consider looting as illegal some peoples coming from 3rd world nations to live with us may not see looting as a bad thing. They have not learnt right from wrong.
Non-immigrant nations do not need to spend the time teaching newly arrived basics to immigrants they can actually take that extra time and money to teach their own more advanced lessons such as how important a good education is and getting good grades.