The Ad Council has a long history of working directly with government.
And, for a long time (including the time period covered here), the Federal Communications Commission required radio and television stations to allocate a certain amount of airtime to "public service," which in practice meant running ads created by the Ad Council ... including this one it created in cahoots with Keep America Beautiful.
Keep America Beautiful claims it's transferring the "rights" to the ad to the National Congress of American Indians, which in turn "plans to end the use of the ad and watch for any unauthorized use."
Even if "intellectual property" was a thing, this ad wouldn't qualify as IP. It was created by government-funded entities for use in government-required programs. It's inherently in the public domain -- "public property."
I neither need, nor intend to request, anyone's permission to use it in any way I damn well please.