And same for all of its subspecies too. So I suppose the simplest guess is that the threatened search parameter is not paying attention to geography, but just looking for any kind of threatened status added to the taxon record. Maybe or maybe not intentionally so, would have to hear from the devs.
Hmmm, but wait, unchecking Threatened returns a bunch more records for the same geographic scope (United States). Remove the geographic scope, and there is still about a 10-fold change in number of records with the Threatened parameter, and still not in places with Threatened status. So yeah, not making any sense to me either.