Why was the chinese empire able to take shape so quickly, while that of the romans took centuries?

By the year 1900 new york city had more than just people of british heritage. there were more people of italian descent than the cities of florence, genoa and venice put together. it was home to more irish than dublin (the capital of ireland) and more germans than hamburg. joining them were many thousands of people of polish, hungarian, and czech descent. what term best describes new york cities changing culture? a a pot of chili b a bowl of sugar c a cup of coffee d a slice of cheese