Some historians have argued that Americans need to study empires because the US is the current big one. Is that fair? Yes and no, I think. The US is more dominant as a superpower today than Britain at its peak. Our adventures in ruling overseas colonies have been relatively limited, though, in both time and space. With relatively few exceptions, we have avoided grabbing up huge chunks of the rest of the world and occupying them in long term fashion. The big exceptions we acquired as the result of WWII (Japan and parts of Germany, plus some Pacific Islands) and most of them we were happy to turn loose fairly early. Iraq was an aberration and is now independent.
We do have a large list of client states, though, countries that are allied with us and under a certain amount of pressure to follow our lead. NATO is one prominent institution of the type. We also have a history of meddling around the world, by military, economic, and other means. For the most part, however, being part of the American empire is voluntary and the client states control how far in they want to be.
Why be part of anybody's empire, anyway, especially if you have a choice? Mostly, I think, for protection. Cortez was able to conquer Mexico with his tiny Army mostly because he found ready allies among the locals against oppressive Aztec power. NATO was built out of fear of Communist Russia. Japan likes us better now that China is an emerging superpower.
In any case, analyzing the entrails of past empires has its own rewards in understanding.