The EIRP is 4 watts in 2.4 GHz band. More than enough to wipe out your neighbors. Also more than enough to get absolutely tremendous range in line of sight conditions.
I can purchase and install an unlimited number of 2.4 GHz Part 15 devices, rendering the band useless to anyone so long as I am attempting to use those devices in a manner consistent with their application. As another Part 15 user, you have no recourse. If a licensed user complains to the FCC, they may decide I have to stop using them and notify me as such. Note: one of my neighbors does this, by having an AP on every 2.4 GHz and 5 GHz channel.
Newest Wifi 6 stuff in the US has a power limit on some spectrum and some usages, but nowhere near as low as what I was hoping for.