Yep, the US does not refine nickel, it is a good point, should have talked about nickel in your OP.The vast majority of smelting capacity was built in the early 1900s or before. Most upgrades corresponded to WWII. Closure corresponded to the moving targets on air quality and water in the 80s by the EPA.
In Montana, Stillwater built a small smelter ( private) but they ship overseas for a refinery. In Idaho the Bunker Hill smelter closed as did the Anaconda smelter. After that the ASARC smelter also closed. I believe Kennecott quit accepting outside ores.
I never worked Arizona and New Mexico that was out of our Denver office so I don't know much about Hayden and other smelters down there.
Oregon lost the Hanna nickle smelter in that same period. Tacoma was closed down with the ASARCO collapse. I don't know if the Missouri smelters are still open but I had heard they stopped being a custom operation before I left the US Bureau of Mines.
If you can take a link to a map of all the copper smelters in the world and us that to draw conclusions about an individual, that says all I will ever need to know about you objectivity.In a political move the US Bureau of Mines was defunded in 1996. The USGS became a cover for the US Biological Survey and all my colleges in the USGS told me that in the 90s they were only allowed to identify environmental problems related to mining. If they are your best link to the mineral industry I can guess where you fit in the bigger picture.
You could have simply taken the map, pointed out that there are only 3 copper smelters in the US and that none of those are in the top 21 smelters in the world by output. That easily supports your case, and half the work was done for you. When a person does not take the time to make a good argument, it says they do not really care about the subject.