Correct, so when I post my song I created to Funkwhale, it’s then federated across the fediverse, living on other servers and able to be downloaded.

AFAIK, the songs do not get distributed across the Fediverse, only the link to the original server.

Someone in the fediverse likes my song and they download it. Who then protects my license and attribution rights beside myself?

How is it different from you hosting your songs on your own website?

How is it different from songs you made available through Bandcamp? Does Bandcamp go chasing people pirating your work and/or using in unlicensed cases (e.g, playing in a commercial setting)?