[elbasti]

Well, to be technical the US does have colonies and territories--the largest of which is Puerto Rico, whose residents have no vote in US elections. There are a number of other small colonies with varying degrees of independence and representation (Guam, American Samoa, and the Virgin Islands).

And of course the US almost in it's entirety owes its size and natural resources to very real "empire building" in the 19th and 20th centuries.

Admittedly the territorial expansion of the US has slowed/stopped in the past 100-200 years, but it's not hard to understand how for someone belonging to a group that lived in a given place for many, many multiples of that duration, the current situation might feel, even today, like occupation. (see: hawaii sovereignty movement, native american reservations)

I suppose the question is "when does an empire stop being an empire?" Is it the day it stops expanding? 100 years later? When nobody remembers how things were "before"? I think it's an interesting question.