It was the terrain of the Bocage country that kept the Americans from breaking through in Normandy. Having a specialist heavy tank wouldn't have mattered when it would have just ran into the next series of hedgerows. Once the Americans hit open country where it could utilize its numerically superior armor and air power, it was a straight shot to the Rhine. Only thing stopping them from going further was that they outrun their supply.
A specialist heavy tank should have made it easier to make it to the next series of hedgerows instead of being knocked out of action like many Sherman were attacking pak 40s head om.