Okay, some replies are quite interesting, unfortunately I seem to be missing a point. Sicarius, you state "America is one of the most brutal empires of all time" (later you rephrase that the thread should've been named "[The] United States is an empire"), this is follows by ten statements: one statement why USA is an empire (#1), some statements why it is cruel (#2, #3, #5, #6), some related statements (#4, #7, #8), one statement unrelated to the subject (#9) and one highly speculative statement (#10).
Well, it's clear that discussing the last two point will not improve an 'intelligent' discussion. Discussing any related statements is also quite useless.
#1 is way too long: simply stating that its interference is affecting and wants to affect a high percentage of the world's contemporary inhabitants is sufficient. Saying America sponsors dictators is 1: subjective and 2: not relevant to your case. This makes -in my opinion- USA imperialistic, and thereby an empire.
However, I stongly disagree with you that USA is cruel. As a contemporary country it might be cruel, the overload of information on every political misstep is huge. But it does not show plays in which either of the combatants dies (Roman Empire), or do you introduce a registration system in order to systematically perform ethnic cleansing (3rd German Empire), or does put (semi-)randomly a part of your population in forced labor camps, without food in the middle of nowhere (Soviet Empire).
And that's even from a USA critic.