I've noticed that the US armored does not actually have any tanks that are capable of taking out (reliably ie, not a lucky shot) a top tier german panther. It would be nice to see better AP AT--maybe an M-18 (the US anti-Armour Doctrine was a bit screwy where they were not permanently attached to a division I think).
It kinda sucks when you have so many points in the end game and literally nothing viable to take on a german panther, I do understand that this fact is relatively historical (they used to send 3 normal Shermans and one firefly/US equivalent) but the US Heavy hitters seem not that hard hiting.
You have to use the hedgerows to your advantage. Either lure the Panthers into a "room" of hedgerows where they get hit at close range as soon as they enter, from multiple angles if possible. Use infantry to guard the flanks of your tanks near hedgerows in case enemy infantry tries to pass through.
or you can peek out from behind a hedge at opportune moments when the Panther/whatever else is close.
Do this and you'll get the kills. You get +1 AP every 100m closer you are. For that, the closer you are, the more the Sherman becomes the superior tank with its cost factored in.
The terrain of Normandy is really their savior here. If there were no hedgerows, Normandy would look like the Russian steppe, and in that case they would be hopelessly outmatched against Panthers.
As it is I think the Shermans are perfectly fine, I have no qualms about any of them. I'm not even that bothered by the cost.
edit: another tip is always have a Calliope but never use the full barrage at once since it takes forever to reload. you can suppress multiple blobs or multiple individual spread out tanks if it comes to that. as long as its within the same 60 rocket load, the aim time will be a only a few seconds. after you panic them, its time to counter attack.
