If your only constraint is cost, there's basically no argument for using a domestic PCB manufacturer or assembly house. You can't beat them. The closest you might get is "offshoring" to Mexico, and even then, you'll probably still spend more than going with a Chinese manufacturer. If you go through Sierra, I seem to recall that they contract with a Taiwanese PCB fab for the bare boards, but I could be wrong. They should have a domestic partner, not sure who, for e.g. ITAR boards.
So why go domestic? For us, there were IP concerns (that we'd already seen with non-electronic products), there were concerns about shipments getting held up in customs, and there were concerns about manufacturing support. If you want boards to be flashed and tested at the factory, so you can dropship your assembled product to whatever its final destination, its very valuable to send somebody to the board house to work with their integration engineers to do it. I ended up spending most of a week commuting to a board house in Fremont in 2021, so I could train up their people on operating the programming and testing jig we'd built, and operating the calibration system we'd built. Driving from my home (at the time) in Oakland to Fremont was much much easier than flying to Shenzen (or wherever), I didn't have to contend with the great firewall, and if something went wrong, I could be over in 45 minutes. All during the California (and also China) Covid lockdowns.
That is what you're getting with a domestic board house, so if none of that is a concern, there's really no reason to pay the borderline extortionate premium to do it.