How is America influencing other countries

Why is it useful for historians to base certain studies on the analysis of historical periods

By the end of the 1800s, there was a change in the nature of the immigrants coming to the united states. immigration from northern europe—england, ireland, germany, and scandinavia—declined, while immigration from italy, russia, and austria-hungary grew. in fact, between 1900 and 1910, more than three-fourths of all immigrants came from these three countries. unfortunately, these countries were far removed england, the home of our founders, and the immigrants who came from them had a hard time adjusting to life in their new country.

Which of these played the biggest role in increased urbanization in the late 1800s? a) transportation improved b) the military was stronger c) no one was farming anymore d) steam power was discovered