probably. look at the US's economic and political agenda, and see whether its policy in foreign countries has any relation. for example, the US wants to make Iraq a democracy, which would serve the US's self-interest.
high school hiistory essays can hover in the "grey area," meaning they can avoid the question by arguing both sides. so you might argue that the US is still imperialistic (Iraq), but not as much as it was in the past (Phillippines, Haiti, Panama, etc.)