Answer:
To a considerable extent.
Step-by-step explanation:
The 20th century saw the growth of America as a global power. Before WW2, her influence was most keenly felt in Central and South America, which had been the case since the Monroe Doctrine. They also had a colonial relationship with the Philippines during this period.
After WW2, intervention in US foreign policy replaced isolationism as the need was felt to contain communism and the Soviet Union, and after 1949 China. This led to far greater involvement in European affairs and direct military action in Korea and Vietnam.
The USA also became involved in conflicts in Africa as well as the Arab-Israeli conflict, backing nationalist movements and governments which were seen as friendly.
Were these relations imperialist. Yes in that they were not based on an equitable distribution of power between the USA and those she supported. American self-interest, both politically and economically was at the forefront of US foreign policy throughout the 20th century.
Examples would include the overthrowal of the Mossadeq government in Iran in the 50's to secure Iranian oil, and the same in Chile in 1973 when the Allende government was replaced in a CIA organized coup by a brutal military dictatorship again to protect US economic interests. The US also supported the Mafia backed Batista dictatorship in Cuba, and right wing death squads in El Salvador and Honduras in the 70's.
US involvement in Vietnam and indeed the illegal bombing and invasion of Cambodia is a litany of disastrous decisions to protect US interests and the heroin coming out of The Golden Triangle through US army customs. The list is endless.