The United States became an imperial power
a. when the United States built the Panama Canal.
b. when the United States gained overseas territory.
c. when U.S. marines invaded the Dominican Republic.
d. when U.S. bankers made loans of $1.5 million to Nicaragua.
Technically speaking, the United States became an imperial power "b. when the United States gained overseas territory", since imperialism implies that a nation is in total control of a foreign land for their own benefit.
