Since we admire New Zealand's model of license free radio and how it works with commercial radio here's the info on how it works...
https://www.rsm.govt.nz/licensing/frequencies-for-anyone/low-power-fm-broadcasting
https://www.radiosurvivor.com/2017/01/new-zealand-legal-unlicensed-low-power-fm/
I like it. I like it a lot.
The Part 15 people who hate FM will say that it would never work, but it would if the FCC and ISED opened up some of the spectrum below 88.1 that is going to waste. It was supposed to be used for wireless microphones, and interestingly enough, with a power limit of 1 watt. I don't think that it's happening all that much.
Just think of the advantages of giving up even 87.5 & 87.7 (maybe 87.9) for low power broadcasting. Many existing radios will tune in those frequencies, particularly the newer ones. No one in their right minds would use the 'senior' band of 88.1-107.9 at much lower power, thus minimizing interference. In fact, you could probably do away with Part 15 in the current FM broadcast band.
One of the laments used by the doomsayers is that radio is dying. Well, then, why not let those who really want to do radio actually do it with a bit of power, say that 1 watt? And if radio is really dying, then there will be less people actually wanting to do it, so the argument that it wouldn't work here because of greater population (compared to New Zealand) goes away. Anyway, any interference generated would have to be dealt with by those using that bit of spectrum (again, as in New Zealand).
I note that all equipment used in New Zealand has to be type approved with an ID. Good. Make it that way here (it's already in force in Canada, a bit of a grey area in the U.S.). That will also go a long way to ensuring minimal interference to existing licensed stations.