The main reason we don't have rare earth mines in the U.S. is that we don't want to deal with the uranium and thorium. Of course there are productive things we could do with those elements, which would also go a long way towards reducing our carbon emissions.
If we do run low on rare earths or platinum group metals, there's plenty in the asteroids. Once we have reusable rockets and can harvest fuel from the asteroids or the moon, mining the asteroids for high-value metals could actually be fairly economical, and would remove the environmental impact of the mining it replaces on Earth.
An argument has been made that one of China's key exports has been its willingness to absorb massive environmental contamination. A practice which seems to be changing, though there may be new marker entrants. Not necessarilly fully voluntary on the part of all participants, most especially those not yet born.
If we do run low on rare earths or platinum group metals, there's plenty in the asteroids. Once we have reusable rockets and can harvest fuel from the asteroids or the moon, mining the asteroids for high-value metals could actually be fairly economical, and would remove the environmental impact of the mining it replaces on Earth.