Coydogs are a myth that seems plausible on first glance. Various people have studied this and all the coydogs turned out to be regular wild canines or their crosses (genetic studies). Although the two species can cross, the studies concluded that the problem was that dogs and their crosses don’t provide for pups in a way that ensures survival in the wild.
Here in Pennsylvania, the first eastern coyotes were thought to be coydogs but they turned out to be wolf/coyote hybrids.
In the south,Red wolves are also hybrids. There is no evidence that they ever were anything else.
Gee, that’s strange, I knew a guy who owned one of those “myths”. Coyote made one of his bitches pregnant, she had one pup that looked exactly like a coyote, was evil tempered and finally had to be put down when it was about 3 years old. Nice to know it was just a myth however.