"... send drywall from there to here more profitably than we can make it and sell it here." Most of that gypsum board was imported in 2 years after Hurricanes Katrina and Rita. Home repairs increased demand above capacity of domestic suppliers or Canadian sources. Much if it I read was made by a German group Knauf operating factories in China. That simply shows that global supply chains might not be fully described by anti-nation slogans.
United States - Producer Price Index by Industry: Gypsum Product Manufacturing - 2025 Data 2026 Forecast 1965-2022 Historical Gypsum price index history. I will interpret price peak mid-2006 as that rebuilding boom, and price valley 2008-2011 as partially resulting from imports. Other interpretations may well exist.
I see a steadily increasing manufacture of gypsum products, but no breakdown of whether the firms that make the construction products are churning out drywall and joint mud to the neglect of their traditional plaster product lines. Don't landfill your scrap drywall! These guys can peel the paper off and get the gypsum back into the supply stream. They're after leftover drywall scrap from new construction. Drywall taken out in demolitions can have all kinds of unwanted stuff attached.
It is my reading that US coal-plant flue-gas desulfurisation with limestone created a big pile, of which little was into made new gypsum panels. Part went to road building and most went to landfills. This coal-plant exit-stuff contains ash with mercury and other exciting ingredients. Probably good that (domestic sourced) gypsum panels have not much of that.