your original post said exist which implied the US was in some inept and couldnt make any. US had the designed and they all completed trials and were ready for production said production never happened, but I guess its just all semantics.
Pershing was a Heavy Tank during WWII and reclassified after WWII because the bar for armor and firepower for tanks had gone up. Saying the Pershing was a medium tanks means both the IS-1 and Tiger I were also mediums as all had comparable firepower armor and roles.
the Pershing was lighter than the panther, at 41 tons.
US high command decided that it would take too much time to refit all the factories and retrain workers to produce the Pershing, not to mention the logistical issues of having a new vehicle that requires different tools, ammunition, etc. when the war was already over basically.
On top of that a majority of the tanks they were seeing didn't require the heavier arms and armor like the eastern front. Perhaps if Japan had fielding something other than a pop can on treads they would have bothered switching production. But I digress...