Therefore, I have come up with a new hypothesis to explain these odd sightings. I feel that there is a species of large flightless bird living in the Americas which has evolved tooth-like serrations in its beak and a long, bony tail. This may sound unlikely, but in reality, it isn't. There are many birds alive today with tooth-like structures in their beaks; one example is the merganser. And there are already many birds which have claws on their wings, such as the ostrich. And finally, there was an extinct flightless bird called Sylviornis which had long, bony tails, just like their non-avian theropod relatives did.
These birds are probably around 5 feet tall and 9 feet long. They have a beak with tooth-like structures in it, which they use to help catch their prey. They are omnivorous, feeding on nuts, seeds, and insects, and occasionally taking larger prey, too. They most likely belong to the order Galliformes, which includes chicken and turkeys, as well as Sylviornis. In fact, they might actually be birds in the same family as Sylviornis that evolved tooth-like structures in their beaks, wing claws, and even longer tails.
So, this is my hypothesis. I would appreciate any feedback or constructive critiques of it. Cheers!