CHICAGO – When U.S. President Donald Trump floated the idea of buying Greenland during his first term, the world reacted with disbelief. It seemed utterly absurd, even comical – an imperial fantasy dressed up as a real-estate negotiation. And yet it is true that Greenland matters, and that its status could have far-reaching implications. The renewed attention on the world’s largest island reflects the view that the world is coalescing into three spheres of influence, centered around the United States, Russia, and China. While some dismiss this geopolitical vision as a Trumpian vulgarity, the troubling reality is that it is neither unique to Trump nor entirely irrational. As the post-Cold War era recedes, a more regional and competitive order is reasserting itself. Large powers shape their immediate surroundings not only out of ambition, but also because they face constraints. The farther outward one’s influence extends, the more geography, domestic capacity, or resistance from rivals starts to matter. Russia, China, and the US are each nuclear superpowers and the largest countr