Under what circumstances did the united states emerge as a world power, and how did the nation respond to this new role? short answer

The control of several countries. The response  was to try to keep this control and work in expansion.

Explanation:

At the end of Century 19th the historians have considered the age of the American imperialism due to the United states did annex Hawaii and took the control over cuba, guam, Puerto Rico and Philippines.  

These circumstances let the United States to grow and be prospered.  The most productive economy was evidenced at the 1890 approximately.

here are some major conflicts i found. maybe pick one and do more research on it. (cause i ain't writing 6 paragraphs)

in 1877, the nez perce war took place.

1881 - president james garfield was assassinated.

1882 - the chinese exclusion act was passed.

1883 - a decision in the civil rights cases legalized racial segregation in the united states.

1887 - the dawes act was passed.

1893 - the panic of 1893 took place. (what a creative name)

and there are probably other topics you can find if you just search up "united states timeline," or "conflicts in the 19th century for america."

then once you find a topic you like find out how it affected the people of america and what not. (sorry if this feels a bit short changed, history was and never will be one of my strong topics)

explanation:

damn girl thats not really your friend then. : /