There is a common culture in every country. It may have different components like regional, political and ethnic differences, but there is always a larger commo

There is a common culture in every country. It may have different components like regional, political and ethnic differences, but there is always a larger common culture. Your view suggests you think that people rigidly stick to whatever culture they're born into, but that's not the case. The longer people stay in a country the more the local culture seeps in. The children of immigrants typically adopt the local culture, even if it has a ethnic flavor. So there is a natural trend toward the local culture. If your view were true countries with permanent large immigration programs such as Australia, Canada and the US would over time become balkanised, but that's obviously not the case. Different ethnic groups tend to an understanding of each other rather than conflict. There isn't naturally friction due to ethnic differences, just like religions don't tend to be add odds with each others members. You don't need to have friends from other ethnic groups, or a particular ethnic group, just like you don't need to have friends in other political or religious groups. Life isn't a bingo card. All you need to do is subscribe to a few common fundamental values, and that's generally easy for people in a given country to do, even if it takes some time.