Very little on White's official page has covered folklore and mythology that might be found in Medieval America. We know there are roughly five spots on a "Here be Monsters" map, indicating Cryptids and their ilks.
The Jackelope is the only page White has written. Jackalopes aren't "cryptids" in the usual sense, in that they are not truly the subject of hunts for real life monsters, but they are a fanciful creature exclusive to Americana.
Bigfoot: The most famous creature in American folklore, and perhaps a top 10 iconic monster period.
Ufo: This is where it gets particularly interesting, as UFOs are strictly a high tech phenomenon more at home in science fiction than a culture that believes in magic
Elvis: Not strictly a monster (though modern day people are starting to find his behavior in life appalling), but definitely a subject of urban legends and supermarket tabloids.
Wizard of Oz is the platonic ideal of an American Legend.
What's also interesting is two of the biggest pheneomenons of the 2010's--Game of Thrones and the Marvel Cinematic Universe. It's seen as rather fitting that both are concluding their "sagas" within the same month in the last year of the decade.