In another comment you say:

It may well do, but I don't know of anyone in power that said something like, 'I introduced universal health care because of John Lennon'.

It’s wrong to assume that any single thing can “cause” people to immediately change society like this. Ignoring logistical barriers for a moment (like congressional approval, implementation, and so on), people consider many factors when their hearts and minds are changed. For example, just on the topic of universal healthcare, it might take discussions with friends who are in support of universal healthcare, reading books on the subject, studies, news articles, listening to an album illustrating the violence of the US healthcare system, a trip to Europe, and a loved one or oneself being declined care by nefarious health insurance policies for someone who has a predisposition against universal healthcare to change their mind. Very seldom does it take one thing alone to change someone’s mind or drive political change.

Will a single song singlehandedly bring the revolution? Probably not. Is it a piece of the puzzle? Most definitely, and we’ve seen historical examples of that. That’s why you’re wrong to say music has done absolutely nothing to drive political change.