According to this article, China could potentially cut off supplies of critical materials needed by large portions of the U.S. economy. In fact, the idea of China banning exports of rare-earth elements to the U.S. is possible. This is big news because U.S. oil refiners rely on rare-earth imports as catalysts to turn crude oil into gasoline.
In addition, permanent magnets, which also use rare-earth elements, are used in wind turbines and electric cars. The problem is that China dominates their production.