To do a "well, actually" I guess we didn't really have an empire until well past the country's founding. We were a mostly irrelevant backwater for some period of time.
ETA: And as someone who freaking loves this country, I realize that saying a comment like the above is one that could probably get you into a fight two days from now, most especially, when all kinds of fetishistic performative military nonsense and uncritical screeds about this country are at peak ridiculousness (and I love July 4th in spite of these flaws). I consider myself a real patriot, but one that is unwilling to whitewash this country.
No, the US has been an empire from the start. Unless you don't count conquering and colonizing the indigenous peoples because they aren't "civilized" or something.