no rubber for seals
Modern synthetic rubber would indeed be unavailable, but I vaguely recall reading something to the effect that early steam engines used leather seals or something like that.
But yeah, there's a lot of missing prerequisites for machinery. Even simple rotary power -- like from a windmill or waterwheel -- would suffer from being incapable of long distance transmission. Such a limit means the interior lands of a country away from a river or coast would remain unusable for development beyond basic agriculture. No railroads, no A/C, no Phoenix Arizona.
At the very minimum, this type of mail would incur the $0.46 non-machinable surcharge because it's smaller than one of the minimum USPS dimensions for postcards, namely that one side has to be at least 5 inches (127 mm exact). You may also have issues with it being too floppy for basic handling by the postal carrier, especially if it was previously left in a warm mailbox.
But perhaps a more practical issue may arise first: will stamps even adhere to the wrapping of a Kraft Cheese single? If you cannot affix postage, that's the most immediate impediment.