Hi Hi Puffy Ami Yumi is such a strange show, I'm not really sure who it's for?
Is it an attempt to get idol culture to catch on in America so Warner Music could expand that market? Well, not really - it has live-action idol promo video-esque segments, but viewers mostly seemed confused by them.
Is it an attempt to court anime fans like Teen Titans did? Then why bother using it to promote a real band at all?
Sam Register even said outright that WB thought the market wasn't there yet like it was for anime. He also implied that it was mostly happenstance that he learned about the band when seeing them interviewed on TV while he was visiting Japan, and he thought a girl-rock show would bolster CN's female viewership (Likely while riding the coattails of the Japanophillia boom, but he didn't say that outright).