Because countries like the U. S. and trace their culture roots to this part of Europe

countries like the U.S. and England  trace their culture roots to Greece.

Explanation:

A lot of cultural values that currently held by western civilizations was originated from ancient Greece. They were the first people that first introduced the concept of Democracy which gave the people with the power to influence the government.

The spread of Greece's cultural value was accelerated with the help of Roman empire. After learning the cultural values from the Greek , People from Rome managed to conquered the vast majority of Europe. They spread the culture to the conquered area throughout the process. Since US was colonized by European countries, the culture got spread in north American territory too.

d.) continue to rise rapidly