There's no reason to treat anyone differently because they're a different nationality. I have no problem being friendly towards anyone of any nation. As for diversity, if you surround yourself only with people of a like mind, you'll never hear a different opinion or point of view. It's only by including a diverse mix of people that you can get the more complete picture to all the world has to offer.
International friendship is an important element because it creates room for help and learning of new developments and technology. Diversity helps to us to understand that each individual is unique, and recognize each other's different ways of life.