I was a farm equipment mechanic for fifteen years, through the mid 70's, eighties, and early 90's
As far as used tractors go, there are some that shine in my memory. One was a tractor that Allis Chalmers marketed. It was a Fiat tractor, that Allis sold as the 5050.
50 Hp, synchromesh trans.
When equipped with 4WD, and Allis's own 500 series loader, it was a solid, and reliable unit, with few luxuries, and quite tough.
That loader is important, some of the after market loaders fitted to this tractor were designed for 2WD power, and would not stand what this tractor was capable of.
John Deer's 1120 was a nice reliable tractor, but was stuck with 2wd.
The old Fords, and Masseys of the 8N, 9n etc. type, and other makes of the vintage, are probably best suited for farm shows and old tractor displays. They do work, and are capable, but they are toys compared to what a 4WD tractor of even a few years newer can do.
They have reliability issues now, and are tinkerers tractors. Hard on gas too.
Kubota tractors are Japanese, true, however, the company now has American plants making some stuff in the USA. Garden tractors, and RTV's at this point, and I think some farm loaders, and mower decks.
With the exception of some garden tractor engines, Kubota uses their own stuff. They rarely out source. You won't find a new Kubota tractor, with a Yanmar or Mitsubishi engine for example. They have their own tier three and tier four diesels. Very reliable.