First, 50% of the component value must be "buy America" qualified.
Next, the final assembly must be in the US.
The final assembly must "substantially alter" the product.
I believe that anything from NAFTA countries qualifies as "buy America."
The commerce department makes the rules on the meaning of "substantially alter" on a case by case basis. Their interpretation is rather (unbelievably) stringent. A major home improvement chain exported US made metal blanks overseas for machining. After machining, the parts came back, were rounded, finished, had the head angle modified (bent), and the handle covered with a rubber sheath. Commerce said that all the finishing, modification of the shape, and covering the handle did not qualify as "substantial transformation" for the hammers.
My interpretation is that attaching a frame and placing a junction box probably is not sufficient. My guess is that laminating, framing, and final wiring of a PV panel would be required to pass muster. But changing a panel to attach an inverter
or a unique mounting system just might do the trick.
Note: I am not a lawyer, this is just what I've picked up from research last year. Be sure to use legal counsel with commerce department and import experience. Interpretations of statutes can change over some pretty short periods too.
Feel free to send info on your panels and other components used in PV installations. I work closely with developers all over the place and could put in a good word for a great product offered by great guys like you!