I asked CZ for clarification - as manufacturers they might be able to import the barrels, as these are new production items, NOT military surplus or "parts kits" like Century was making the ROMAKs out of. Those have to use US made barrels. Also, I've fired a few US made rifle barrels over the years that were quite good.
My BREN seems to shoot quite straight for me, however, I am not legendary shooters, but the consensus seems to be quite accurate and reliable.