Happiness and harmony is not based on the nation-state. There are plenty of nation-states around the world that are not happy nor harmonious but perfectly sovereign. Government, whether local, state, national or international does not make the people happy nor harmonious, it is not something the government has the power to do. It can only take and grab and harm.
That which governs least, governs best. Less government power, less government wealth, less government interference is what will increase happiness and harmony.