And more than maybe anywhere else, that idea is embraced in the United States, where the mythos of the land of opportunity is practically part of our foundation.
And then in the hour of midnight, the primal fall was repeated and represented, and the awful thing veiled in the mythos of the Tree in the Garden was done anew.
As a product of the Tulpa Effect, Slenderman's abilities can be hard to pin down because they are typically ever-changing as new beliefs about him- or it- are added to the current mythos.
It's far too late to simply try to convince people Slenderman doesn't exist- too many already believe it does- but you can add to the Slenderman mythos and create ways in which it can be defeated.