As far as I know the Sherman was a pretty good tank. The 75 mm Sherman has the advantage of better turret layout over the T-34-76. The 76 mm gunned Shermans were at least on par with the T-34-85s.
I am not sure about training and experience however. From what I've read though the Soviet tank crew training was not entirely satisfactory during the war. From what little I've read about US tank battles (e.g. Arracourt) they seemed to do very well against superior tanks (in armament and armor), though perhaps I am focusing too much on that one battle.
I would put them somewhere between the Soviets and the Germans, both in infantry and armor. Perhaps 3 to 4 in attack or defense for infantry units. Armor should be better than the Soviets in pure numbers; of course, the US will lack heavy tank units to attach. I am not sure how their specialist artillery steps would be treated. Though I would love to see M7 priests with +3 artillery shifts