I suggest reusing the already existing model of the american Sherman M4A1 (76mm) as a new medium tank for the americans. It could be used as a tank with "medium type" armour and "heavy type" gun, categorised as a "medium tank" and costing 300 to 400 fuel. This means it can penetrate heavies and kill them with 2 shots and it can one shot enemy mediums. Enemy heavies would only need 1 shot to kill it. Enemy mediums would need 2 shots to kill it.
Since the model already existed and was replaced by the current Sherman M4A4 it would be a nice addition with few effort.
