A 40' container has 2390 cubic feet of volume.
It costs ~$10K to ship from China to the USA.
4'x8'x1/2" sheetrock is 1.33 cubic feet.
That's about 1800 sheets of sheetrock per 40' container.
That's about $0.55 per sheet in shipping.
Even small gains on labor, material and energy costs will quickly dwarf the shipping costs.
I'm not advocating for China based production, I'm just doing the math.