I wonder if they really tried to replicate how Americans would have talked at that time. Basically the accent sounds Irish to me, which is not surprising given the number of Scots-Irish(Protestant Irish)that had come to America at that point , and the fact many leaders of the revolution were of that background(Patrick Henry being one). Also indicated by the reference by the leading character that certain revolutionary folks from the other town were “Presbyterians.”
They didn’t, as you said this morning, “screw reality.”