Maybe you haven't dealt with the servo-motors area much.
Parts is parts.
Your component-suppliers... likely utilize raw material (comes in a powder form) from wherever. [ Do your shippers tell you where their fuel to do the shipping comes from...? No. ]
Furthermore, the stringency you are assuming isn't real-world. Specifying 'domestic' materials is not consistent with the 50% domestic content on overall system sourcing for defense contractors. Remember when House Armed Services Committee Chairman Duncan Hunter tried to up it from 50% to 75%? The Shit Hit the Fan at the White House. The President threatened a veto...(his first and only such threat until the Dubai Ports debacle).
The DOD would not so restrict a contract on components derived from rare earths. Quite a number of materials supplies are just not in the U.S. Chromium for one example. And Titanium for another example. Remember when the SR-71 was built? We bought most of the titanium for its fuselage on the sly from the Soviet Union. I doubt they ever would have sold it if they knew what a major advantage we were realizing from their sale...
The Chinese on the other hand, know precisely how critical these super-magnets are to our aerospace, with superior power to weight ratios and vastly greater resistance to heat and vibration. The Chi-Comms have been manifesting all the classic signs of trying to monopolize the supplies of the ores. They tried to snap up UNOCAL last year. And Deng Xiou Ping openly bragged of making China the "Saudi Arabia of Super Magnets."
And a big Part of that "glut" in the market another freeper alludes to is...a product of Chinese dumping to dry up the foreign operations...drive them out of business. He also alludes to infringing on the patents...well guess who is the biggest infringer of all. Yep. China. Puts further pressure on the survival of U.S. and Western supermagnet operations...with their intellectual property interests in the dumpster.
And the U.S. government is frankly AWOL when it comes to IP enforcement against China...or protecting our defense and security industrial supply-chain.
Maybe you haven't dealt with the servo-motors area much. Parts is parts. Your component-suppliers... likely utilize raw material (comes in a powder form) from wherever.
Actually our company supplies it's own servo-motors, synchros, slip-rings etc etc.
So our Purchase Orders don't require anything more than general certs of conformance with each shipment. Nothing would get through inspection if we had to review the massive amount of paperwork needed to verify materials and processes for every single item that goes into something like a motor.
However we have been supplying Boeing, Lockheed Martin and the DoD for many years, and the domestic material requirments are becoming more of an issue lately.
In anycase where DFARS has been applied to our inspection process, the closest I've ever come to material from China was rejecting some alloy steel from Taiwan.
Of course there are numerous countries allowed by DFARS that are not necessarily domestic, when it comes to specialty metals, including France and Great Britain.