Except that with the fantasy tanks the Russian get in the game, the M1 is at a qualitative disadvantage. So you get double whammy'd. You have worse tanks, and less of them. American units should be at least twice a numerous and twice as effective if were going to be realistic. M1A4 shoudl being game to balance the T-90AM.
Well then you got a lucky round in that match for sure. Usually it takes at least 5 Panthers to stand a chance against a Sherman. Hitler commissioned the King Tiger specifically because the Panther was no match for the M4 most of the time.