I think Massey was one of the first to use the world to build a tractor. Engines from England, transmissions from England, France, Brazil, maybe more, rear axles England, France, Brazil, maybe more. All was shipped to Detroit where the front end, hood and fenders were added as the engine, transmission, and rear axle was assembled. So assembled in the USA back in the 60's and 70's. Then most assembly was moved to England for the small tractors and France for the bigger tractors. The original compacts (205, 210, 220) also certain AC models were built in Japan by Toyosha (note NOT Toyota). Toyosha went up and then the new 4 digit models were built by Iseki
John Deere was using German factories before most realize.
IH I believe with the B414 started with English built tractors
I believe during the 70'5 and 80's White used Fiat (MM, Oliver, Cockshutt and AC) then later used Iseki for some of their models.
So in the end unless you go way back say 40's or 50's it is very hard to find a tractor that was manufactured and built in the USA.
Cheaper to build overseas and ship here than to build here.