production system today, many manufacturers will start to slow down to stop production in about 3-6 months time.  After 6 months, most manufacturers will grind to a halt.  NO output.

For light rare earths, the U.S. will need 2-3 years to find resupply of the raw materials.  But you need to process those raw materials before you can use them, and currently there is NO processing plant in the U.S.  Thew quickest project is at least 3 years away if you are lucky, and it's only for some, not all, light rare earths.  Exploring a new mine usually takes 7-10 years to find, 10-15 years before you can bring it online and start to produce.  If stealing China's patents, a new processing plant is at least 3-5 years away.  Without stealing, we are talking about 10-15 years time.

For heavy rare earths, all bets are off.  There are just very little to none existing outside of China.  The heavy ones are the most important for the defense, aerospace, auto, mechanical, metallurgical industries.  In other words, all these industries, which form the very foundation of the U.S. military power, will all stop producing and there is no way to recover!  Tell me if you are in the WH, will you worry?  Or, maybe Trump is not worring, because he simply doesn't understand or believe it!