If we depend on one country (e.g.China) for a critical input (e.g. rare earth minerals) which are essential for a broad category of industry (e.g. magnets for electric vehicles and railguns), then that country could cut us off during war (as China plans), or take over the businesses that use these materials, by denying them to competitors (as China has done).
Most of the US’s strategic mineral mines were converted to parks long ago (Clinton era) else areas were closed to exploration.