I've heard that it could cost well north of a trillion to actually wean off China's supply, if it's even possible: this stuff is key to military strategy, and the US dependency on rare earths from China prevents it from being able to attack China militarily. So China's obvious move, if the US is remotely serious about extricating itself from dependency, is to use the same export controls the US has leveraged on AI chips. Endgame in an escalatory path is US high tech, including the defense sector, being hollowed out.

On top of all this, the rare earths industry in China has a serious patent moat. The US would likely need to violate patents to match China's level of production, which would basically be a huge gift to China since they'd then be justified in doing the same.