Why can culture regions extend beyond the border?

Borders are created by men. Culture is generated by the situation in which people live together for generations. When people from different cultures live together for generations, they are bound to influence one another. So culture is evolved and borders are created. For example the Indian subcontinent is culturally one for centuries. But it is divided by borders now. With the onset on internet, the world is getting united culturally. There seems to be clashes of cultures through out the globe, at present. That is inevitable thing for the integrations of the cultures. You will have the better and integrated global culture. There will be unity in the diversity across the globe. The borders will disappear eventually. One day visa will be a formality for most of the people.