For a while, to find "America's Best Music" on iHeart, the only option was WNAM in the Appleton, Wisconsin, market. It's a Cumulus station and all Cumulus properties are on iHeart. There had been a few others but they either dropped the format or discontinued their iHeartRadio participation.
Now I see KVRE 92.9 in Hot Springs Village, Arkansas, is on iHeartRadio. It has local programming from 6 until noon CT. But after that, it carries America's Best Music. You won't find it by putting America's Best Music in the search engine, since it doesn't use that slogan. It calls itself "Central Arkansas' Best Music."