What happens when the United States decides it can no longer depend on China for some of the world's most strategically important minerals? For mining companies like USA Rare Earth (USAR -0.91%), the answer could be a once-in-a-generation growth opportunity. As Washington endeavors to break China's dominance over the rare-earth supply chain, this American company has suddenly found itself at the center of a much bigger geopolitical struggle. And as that struggle plays out, the question becomes more interest ...