culture region
Well, several countries within Europe share similar cultures, usually distinct to a region. For example, the culture of the Nordic countries are very much alike, as well as the culture of Russia and its past Soviet states (mostly Belarus and the Ukraine).
When countries share a border, it is called a "land border" or a "physical border".
People from diverse backgrounds share their culture by teaching their friends about it. One cans share their culture by cooking native foods for friends, teaching them about: traditional dances, standard greetings/interactions, traditional clothing, and sharing pictures from the countries they originated from.
A community of people who share a common culture is called an ethnic community. It is characterized by individuals who have common traditions, beliefs, language, and practices that set them apart from other groups.
culture
Their culture.
nation-state
Practically every country in Western Europe (UK, Ireland, Germany, France, etc.). These countries share the Western culture.
political culture
a group of societies (e.g.: countries, villages, cities) that share the same: -territory -language -culture -architecture -religion
we would all share the same language and the same culture and eat the same food and probably have the same aspects as other countries.
a group of societies (e.g.: countries, villages, cities) that share the same: -territory -language -culture -architecture -religion