Here's another shot of the vehicle in question. It is located "somewhere in

I don't exactly know what the vehicle is, in terms of an exact nomenclature - but I believe Casey had it mostly right, in that it is a "Na Ispug" or "Terror Tank" of the types built in Kharkov, Stalingrad, and Odessa during 1941-42. 1IDVet was going in the right direction with his mention of the Disston Tractor Tank, while Casey specifically mentioned the Kharkov KhTZ-16,. Those vehicles were built on the chassis of the STZ-5 artillery tractors, whereas this specific example is not. There is a KhTZ-16 in a Russian military museum in Kiev. Eagle 1, Spanky, and Argent did what makes these posts fun. RetResMike was just insulting [pout].
Not a lot of info around there, but I think you guys were also hitting close to the mark when you mentioned it might be a movie tank - it may well be a reproduction "Na Ispug" made for a movie (see last link, above) which would explain the non-useful mounting of the main gun, it seemingly having no provision for elevation.
Anyway - necessity is the mother of invention - and it happened here, too, though unlike the Soviets, none of our armored tractors ever saw actual service. Having driven a regular farm tractor over rough terrain, I can only say - Thank Heaven! I can't imagine too many more uncomfortable ways to waddle into battle and die quickly to no purpose other than using up some of the other guy's ammo.
In the US, Case built at least one version of an armored tractor, though in this case the armor was just to protect the operator, and not intended to turn the tractor into an armored fighting vehicle. John Deere, on the other hand, had a couple of models of machine-gun toting tractors.
So, having offered you some more obscure military trivia for your kit bags, I'll close this out with a nice portrait of a couple of the Deere company's products.

Mind you - John Deere products are still being used as the basis for armored tractors, if more along the lines of that Case tractor up above.
Odessa and Kiev are both in the Ukraine.
Heh...
P.S. I'm thinking that John Deere might be taking that Cows with guns video a tad too seriously.