In ww2 combat showed that a specialist breakthrough tank was needed and the heavy casualties Shermans suffered to pak 40s (biggest killer of US tanks) the weeks after D-day could have been avoided if the United States of America had a breakthrough tank. The greatness of US artillery helped the US Army but artillery bombardment always left plenty of surviving hidden paks alive who were able to defeat US tanks and without direct supporting fire from tanks US attacks often failed leading to the Americans being stuck not far from the beaches for a long time despite having complete dominance in both the skies, numbers and in artillery.
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.