abscott,
There's also an exception for COTS -- Commercially Available, Off-The-Shelf items. The test for "Made in America" does not depend on the source of the components if the product is sold to the government (or government-funded) project) in the exact same form as other private purchasers may buy it. Note: this is only as long as the product is substantially transformed in the US.
It can be argued that assembling a Japanese actuator onto an Italian valve body with Korean linkage creates an automatic valve -- a substantial transformation. Neither the actuator, nor the linkage, nor the valve body could serve the purpose of controlling flow from an electrical or pneumatic signal. The assembly can do so, so it's substantially transformed.
I'm not going to pass judgement on the argument -- but I do know it has been used successfully many times.
It's a lot easier to prove (if you win the argument) than the exceptions that deal with lack of availability in the US.
Final note is that the assembly must take place in the US (or one of the Free Trade Agreement countries).
Don't take my word for all this -- you'll really need to get the provider of the assembled valve to stick their neck out and swear to it. Of course, if it's just a plain manual valve, all bets are off. If you resell something in the exact same form in which it was imported, it's not domestic at all.
I marked this thread hoping to find a domestic valve body myself...
Good on ya,
Goober Dave