I pulled out high school history textbook, "The American Nation - A History of the United States" by John A. Garraty (https://en.wikipedia.org/wiki/John_A._Garraty ) to see what it says on the topic. It's from 1979, and is an older edition of the textbook I used in high school.
Chapter 22, which we never reached when I was in HS, is titled "From Isolation to Empire". The last section is titled "Non-colonial Imperial Expansion", and it's relevant to this topic:
> If one defines imperialism narrowly as a policy of occupying and governing foreign lands, American imperialism lasted for an extremely short time. With trivial exceptions, all the American colonies - Hawaii, the Philippines, Guam, Puerto Rico, the Guantanamo base, and the Canal Zone - were obtained between 1898 and 1903. In retrospect it seems clear that the urge to own colonies with only fleeting; the legitimate questions raised by the anti-imperialists and the headaches connected with the practical management of overseas possessions eventually produced a change of policy.
> ... the Roosevelt Corrollary and dollar diplomacy signalled the consolidation of a new policy. ...
> Yet imperialism can be given a broader definition. The historian William Appleman Williams, a sharp critic, has described 20th-century American foreign policy as one of "non-colonial imperial expansion." Its object was to obtain profitable American economic penetration of underdeveloped areas without the trouble of owning and controlling them. Its subsidiary aim was to encourage these countries to "modernize," that is, to remake themselves in the image of the United States. ...
> Examined from this perspective, the Open Door policy, the Roosevelt Corollary, and dollar diplomacy make a single pattern of exploitation, "tragic" rather than evil, according to Williams, because its creators were not evil but only of limited vision. They did not recognize the contradictions in their ideas and values.
So there too you see that the US had an empire, in practical terms, and depending on the definition, that imperial policy existed for more than a few years.
Chapter 22, which we never reached when I was in HS, is titled "From Isolation to Empire". The last section is titled "Non-colonial Imperial Expansion", and it's relevant to this topic:
> If one defines imperialism narrowly as a policy of occupying and governing foreign lands, American imperialism lasted for an extremely short time. With trivial exceptions, all the American colonies - Hawaii, the Philippines, Guam, Puerto Rico, the Guantanamo base, and the Canal Zone - were obtained between 1898 and 1903. In retrospect it seems clear that the urge to own colonies with only fleeting; the legitimate questions raised by the anti-imperialists and the headaches connected with the practical management of overseas possessions eventually produced a change of policy.
> ... the Roosevelt Corrollary and dollar diplomacy signalled the consolidation of a new policy. ...
> Yet imperialism can be given a broader definition. The historian William Appleman Williams, a sharp critic, has described 20th-century American foreign policy as one of "non-colonial imperial expansion." Its object was to obtain profitable American economic penetration of underdeveloped areas without the trouble of owning and controlling them. Its subsidiary aim was to encourage these countries to "modernize," that is, to remake themselves in the image of the United States. ...
> Examined from this perspective, the Open Door policy, the Roosevelt Corollary, and dollar diplomacy make a single pattern of exploitation, "tragic" rather than evil, according to Williams, because its creators were not evil but only of limited vision. They did not recognize the contradictions in their ideas and values.
So there too you see that the US had an empire, in practical terms, and depending on the definition, that imperial policy existed for more than a few years.