Re: "Rare earth" elements -- US readiness
TL:DR: Crikey this is a long post. I advise skipping it.
I don't know this subject well, but I understand that there are 16 rare earth elements (henceforth REEs), useful in varying degrees.
The US mine at Mountain Pass, California, extracts bastnasite-(Ce) ore -- hard rock mining. Right now any ore they dig up is sent for processing to... wait for it... China. I'm not sure what minerals Ucore found at Bokan Mountain, Alaska, but the REE deposits there appear to be hard-rock mining as well. The mine is a long way from production.
China's largest mines (mostly) extract lateritic ores -- essentially, tropical and sub-tropical soils (or paleo-soils; the climate doesn't have to be tropical today). These soils have been heavily weathered and leached in ways that concentrate REEs in near-surface lenses. Mines in Australia, Brazil, and Madagascar also dig up laterites. (Africa, surely? Dunno.)
Laterites are relatively easy to dig up, and the REEs they contain are (again, relatively!) easy to separate. Easier than the hard-rock monzanite and bastnasite ores, anyway.
The ore from Mountain Pass produces primarily cerium, lanthanum, neodymium, and praseodymium, with other REEs together making up only 0.4% of the yield. (USGS publication.)
Chinese lateritic ores produce substantially more samarium, gadolinium, dysprosium, erbium, ytterbium, and, especially, a large amount (relatively speaking!!) of yttrium. (Ibid.)
A quick Google doesn't find references to lateritic rare-earth mines inside the US. There is speculation that some paleo-laterites in Georgia may be valuable, but there appear to be no identified exploitable deposits. Let alone any mines ready to go.
(Sorry, but I think geology is one of the coolest things going. Can't help myself. Found a tiny vein of asbestos in the mountains once, got all excited.)
The obvious point is, no single country has a full complement of the resources necessary for high technology. Therefore globalization of supply chains is mandatory.
The Chinese have been playing the trade-war game with sangfroid, IMHO. They have not weaponized the trade in REEs, nor have they directly attacked the US service economy (I think). (The US has long since slipped from a primarily agricultural economy to an industrial one, and gone on to become a service economy -- read, "business solutions", banking, distribution of goods... Microsoft, Amazon, JP Morgan Chase, that kind of thing. I wrote "primarily". Yes, ag and hard industry remain important.)
The Chinese seem to be holding themselves in reactive mode. Unlike Trump, they seem to be wary of burning bridges.
Obviously, they are cultivating ties with Russia. Putin is reciprocating. They are lowering trade barriers to countries other than the US. They are pushing hard on the RCEP trade agreement, which, if ratified by all proposed members, would create the largest economic bloc in the world. It would be one which excludes the US.
These are flanking moves with the potential to alter global economics for a long time.
The Chinese strategy makes Trump's tactics look ... well, childish. Stupid. It appears that Trump is the way the largest economy in the world enables its own replacement.