I agree with this, although the Americans didn't set out to be a world superpower. Their position in the lead up to both world wars was one of isolationism. Int he wake of the second world war, America found it had no choice to become a superpower because Britain was too indebted and too damaged, and the Russians were threatening what we nowadays call "western" polity. They became a superpower because they had no choice.
I think up to the world wars, America was both in an isolationist mood and expansion. Both ideals were in conflict and the American authorities were engage with both sides. The Americans fought with the Mexicans, Spaniards and Philippine Natives. The US acquired several island kingdoms, notably Hawaii but also several territories around the Pacific and Caribbean. They bought land from Russia, which resulted in Alaska, and much earlier, bought land from the French, which resulted in almost 1/3 of the country's current size. Along with many other conflicts with the Native American tribes, which came from both the civilian and military sectors.
Some Americans didn't want an empire but there were some who did.
A lot of the isolationist momentum was among a small group of intellectuals who were very expressive in their writings. It was true that around both World Wars, many Americans at that time did not see it as their struggle, but there were some who did. IMO, I think the biggest reason why the US didn't barge right into the fight(although there are rumors many people knew they will be brought into the wars one way or another) was that many Americans underestimated their capabilities to begin with. Especially with industry, resources and their relatively safe geographical location were advantages.
In some ways, yes, it's true that the US didn't set out to be "the Hegemon" and it was significantly the result of inheriting the responsibilities of the other empires. However, many Americans were already working on several forms of expansion before gaining their important roles in the world.