MIC and other human intervention aside. YES, there is fundamental inequality through mother nature herself. From the physical traits of human to human, from region to region. The economic, monetary, and natural resource opportunities from family to family, country to country. Throw in human preference and yes, the world is not a monolith in any way shape or form outside of the need for food water and air.
Nationalism like communism is neither good or bad. It's merely an ideology that the people backing it determine it's efficacy. Regarding my love for America specifically, my 'nationalistic pride' hinges on the framework of the founding fathers and the rights explicitly stated in the Bill of Rights. These are positives for humanity. The modern examples we have for government, their proclivity towards corporatism and globalist interests above it's own citizens, is why I hate America.
I never said people should be divided, I'm saying we naturally are, and should not ignore that reality by trying to conform society to how you envision it because it has shown to lead to massive suffering and death. Everything starts with the individual and grows by proximity. From yourself, to your family, your friends, your neighbors, your city, your county, your state, your country. Any other focus of order is simply wrong.