Umm....Doofus....
The USA has never been an imperial power.
Unlike Britain, spain, france, portugal, japan...
well, there were the possessions we took from Spain after the Spanish-American War - we owned the Philippines until after WWII, ruled Cuba for 20 yrs before allowing Cuba independence, still rule Puerto Rico, Guam, and The Caroline Islands, we had special concessions and treaty ports in China much like the other foreign powers in China from the 19th century onto WWII ..., all these were under direct USA's rule until their respective independence and / or restoration to the soverign power / or legally *normalized" as *special* US territories such as PR and Guam are today.
How about the Heyday of the Roman Empire...lets not forget that little delight