Yes, China could leverage us into a short-term crisis in regards to rare earth elements (REEs).   However, and in the long-term, they will have to manage their advantage judiciously lest they risk accelerating competition from newly evolving sources.

https://interestingengineering.com/rare-earth-mineral-deposit-that-can-supply-the-world-found-in-japan

https://interestingengineering.com/scientists-refine-rare-earth-elements-from-mining-waste

Moreover, and to my understanding, the main concentrations of REEs at Hay Mountain lay below the other potentially economic minerals and would be the last to be exploited.  That means from several to scores of years following the start of mining, which we are not about to see anytime soon.  

I am not saying this is not an issue for now as it certainly is.  Besides, drilling proving the presence of a rich source of REEs (along with other metals) could be a promotional bonanza for the company under geopolitical conditions as could be provoked by China.

In any event, drilling has to be our first concern.

VP