So we've got this huge military and are intent on building an empire, but we're going about it all wrong. Why would we want Afghanistan as a possession? It's a dung heap, and it's on the other side of the planet. Iraq at least has oil, but we can buy Iraq's oil the same as anybody else and don't need to occupy the country, an expensive proposition, to get it. The Romans didn't run off conquering distant lands until they had conquered nearby lands, and we should follow their lead.
Let's take Canada and Mexico for starters. And the Bahamas. That way, we would save money on transportation and logistics and wouldn't have so much of a problem with the language and culture. We'd still get practice for our youth as bullet stoppers, and military contractors and suppliers would still be fed. Better yet, we'd get to practice fighting in all kinds of climates and terrains instead of just all desert, all the time. The Navy might even see some action.
Americans could colonize and Americanize the conquered territories as they are pacified.
Eventually we'd take over the whole hemisphere at which point we should probably just stop for a while and consolidate our gains.