Were-Creatures

The legend of the Werewolf is one of the oldest in Western civillization, trying to the wolf's status as an apex predator that haunted the wilds of Europe. It has gone on to reach the shores of America, with the creature being one of the core "classic" monsters in the horror genre. There's something of a wider variety of predators in America, and even further when you go in the Americas. Historically, the nature of nature of "were creatures" was a complete compartmentilzation between beast and man. A werewolf was either a man or a wolf, there was no bipedal but beastly intermediary. This was the case for European Werewolf stories, as well as found in the "skin-changer" stories from Indinginous Americans. For various reasons, American spins on these stories would veer towards a hybrid creature. I've mentioned before the nature of how "mutant" might become a catch-all name for animal human hybrids, although there probably should be distinction between humans who, through some kind of curse and sorcery, and one might say, a sub-species that combine human/animal attributes. (Though it should be said such categorization for the supernatural is a relatively recent human development. And the "were-jaguar" of Olmec motifs also blurs that line.

So what kind of other "were-creatures" would populate Medieval America, and would they supplant the Werewolf in this culture? Other canines in the America are the fox (Which are very common in Japanese folklore, but take on different connotations) and the coyote (Which may be somewhat less regarded than wolves) Were-bears would likely be extremely common in folklore, especially as their range in North America is more extensive (Though White has said wolves have since expanded since The Collapse). That they can stand upright may also evoke the link between bear and man, although in turn may make them less...evil than werewolves, the idea that a bear bridging that gap is somehow less unnatural. The ability to turn into cats is also extremely common throughout the world is quite common, even more common in world myths that have a wide variety of big cats. (Interestingly, there are very few cases of "were-lions", as if the western conception of the lion ahs made it too regal, even sacrosanct, to be the subject of unnatural transformations. The cougar, and as mentioned, jaguar are possible candidates, though bobcats are likely. It may be possible that, as in modern pop culture there's a tendency for feline transformations to be primarily female, that might find its way into the folklore.
There's various flying creatures, though through myth, the transformation into a bird is seen as more whimsical, and less sinister than other shapeshifting, although the owl might be an exception. (It should be said the so-called Mothman is actually more evocative of an owl than a moth. And then of course, there's vampires. Actual medieval stories of vampires could do no such thing--they were actually more akin to zombies. But as the connection with vampires and bats has come much more indelible (brought on the the vampire bat of the New World). Here, the lines between vampires and werewolves may become more blurry, or they might take on the rivalry that itself become part of the modern myth.

Perhaps the the most unqiue addition to folklore in the new Middle Ages is reptillian humanoids. They were not completely unhead of in myth and legend (For instance, the Naga), however for the most part the manifestation of our revuslion to reptiles is found in the dragon. Things like the works of Robert E. Howard, Sleestaks and the urban legend of "lizard people" (which should be said sometimes has xenophobic connotations) is a new interpretation. It's quite possible the idea of serpentine creatures taking human disguises is an ever-present fear, one the Non-Denominational Church may disavow (Much like how the Catholic Church actually discouraged the belief of witches until the early Modern Era.), but the the populace, these remnants of conspiracy theories and UFOlogy live and filtered in this new, more superstitious time. It should be said that in many of the above cases, a human that can transform into beasts was originally a human, but, in the popular imagination, the being was always a reptile first, and in fact, the human form is not a transformation, but a facade.