The core technology is the design and how to make the pieces, not how to follow assembly instructions.
The core technology is in the engines (US built,) the refueling boom (US built,) the wing and centerline refueling hose and drouges (US built,) and the military-specific avionics (US built.)
The fact that Boeing can rebuild wings for the Fairchild Republic A-10 tells me that the sheet aluminum ain't all that complicated.