While that's a valid interpretation of "change history" I would say it is far from the only one. I suspect it is quite common for a song to *help* bind a loose collection of individuals and small group groups into a single group with a cause which can then go on to do dramatic things, but it is near unheard of for a song to initiate such events.

Then there's the "Seeds of Love" effect. Whatever you think of C# and his influence on collecting folk song, promotion and all the rest, his effect is certainly important. If someone else had done it - for example if Kidson and co had been left to their approach - we'd have ended up somewhere else. So undoubtedly the song did change the world, but even the most enthuiastic would be hard pushed to describe it as a dramatic event.