not sure what you are saying, CC - I realize that the polygamy prohibition was originally directed at the Mormons, who no longer practice polygamy. Muslims coming into this country may be bringing multiple wives - who knows.
That’s why I’m thinking it would have been a means of keeping muslims out. Mormonism was born in America so they wouldn’t have been likely immigrants into the country. And as you said, polygamy was already fading among them by 1912.