The U.S developed a heavy tank at the end of WW II, but never fielded it. I saw one at Knox in ‘68. It was huge. The first Pershing [?] tanks, with 90mm cannon appeared at the end of the war in Europe. It was the ONLY American tank capable of a one on one with a Tiger or a Panther. Shermans, while mechanically reliable, and massed produced, were junk.
That's entirely possible. My paternal grandfather was a supervisor at The Budd Company in Philadelphia. During the war he worked at "The Tank Plant" which was a new facility to construct... Tanks. In peacetime The Budd Company stamped metal components that went into car bodies for Chrysler, AMC & Ford Motors. They also had a division that made railcars.
Eventually they were bought-out by Thyssen Steel in the late '70's, early '80's time frame.
I think there's only 1 documented engagement that I've seen between an M26 Pershing and a Panther right at the end of WW2.
The Sherman was a pretty good tank when stacked up against the Mark III & Mark IV Panzers -- these were its true developmental contemporaries. Mass production decisions pretty much precluded a better design entering the pipeline until late-'44. As you say, it didn't show well against the Tigers or Panthers.