I've bought NOS parts from Autozone and Rock Auto. All were in beat-up boxes, and some had light surface rust, but they were functionally perfect. And made in the USA by Moog, Wagner, etc!
Also got lots of gaskets from Rock Auto, including Fel-Pro brand, for small block water pump, t-stat housing, fuel pump, etc, usually for 10-20 cents on the dollar!
They occasionally send me e-mails about "wholesaler closeout" specials and "private label" parts like the CarQuest master cylinder I bought that is USA made. I even see internal engine parts, such as a single piston, single rod bearing, etc. I think they must buy inventories from parts stores that went out of business, including a bunch in dusty old boxes with faded printing.
Right now, I see an 82 passenger-side power window regulator for $15.17. It's Dorman 740516. May not be USA-made, but probably the same as most others costing $40 or more.