For obvious reasons they are always going to need their own fab to some extent, because some applications are just too low volume or would leak way too much project specific information. Wherever the truth lies, I'm sure nothing coming out of there is general purpose computing meant for typical nsa run systems.
It's not too hard to figure out who they're using for mainstream chips and mid size run custom fabs. Look for well established strong us based companies that use us designers that have good analog and small cmos process digital fabs that are located in the US - especially new york, texas and oregon.
That's from 1998 , when building fabs was cheap. I wonder what manufacturing process their latest factory uses.