This is to ignore the entire political culture of the United States and it’s history. Any hypothetical “communist utopia built on depopulated land” would have to have, at some point, contended with the history of how that land became depopulated in the first place, and the accompanying ideology of colonialism, expansionism and capital accumulation which enabled that, in order to become a “communist utopia”. Otherwise, failing to contend with that history, it would not be a “communist utopia” and the ideological descendants of those who carried out the original genocide, depopulation of land, and capital accumulation would still be in charge, most likely trying to expand their empire and methods of subjugation globally. Oh wait, that’s exactly what’s going on in the USA right now! I’ll just quote an excerpt from Samir Amin’s Revolution From North To South to illustrate the point further:

The political culture of the United States is not the same as the one that took form in France beginning with the Enlightenment and, above all, the Revolution. The heritage of those two signal events has, to various extents, marked the history of a large part of the European continent. U.S. political culture has quite different characteristics. The particular form of Protestantism established in New England served to legitimize the new U.S. society and its conquest of the continent in terms drawn from the Bible. The genocide of the Native Americans is a natural part of the new chosen people’s divine mission. Subsequently, the United States extended to the entire world the project of realizing the work that “God” had ordered it to accomplish. The people of the United States live as the “chosen people.”

Of course, the American ideology is not the cause of U.S. imperialist expansion. The latter follows the logic of capital accumulation and serves the interests of capital (which are quite material). But this ideology is perfectly suited to this process. It confuses the issue. The “American Revolution” was only a war of independence without social import. In their revolt against the English monarchy, the American colonists in no way wanted to transform economic and social relations, but simply no longer wanted to share the profits from those relations with the ruling class of the mother country. Their main objective was above all westward expansion. Maintaining slavery was also, in this context, unquestioned. Many of the revolution’s major leaders were slave owners, and their prejudices in this area were unshakeable.