I yodel when it fits the song. I yodel when it don't. I yodel when I'm driving. It definitely is Trad in the US as well as many other cultures.

Jimmy Rogers was not a great yodeler, Roy Rogers was. Bill Staines, Don Edwards, and Suzy Boggus are among the best in the US right now.

Find some very early Sons of the Pioneers recordings for great 3 part harmony yodels.

Pete Seeger, Cisco Huston, Slim Carter, Patsy Montana, all yodeled so it must be trad.

Don