Yeah.looks like you had the same scene as in Oz,with mass importation of illegal AM & later SSB radios.
It really ramped up when the USA went to 40 channels & the manufacturers were stuck with tons of 23ch radios.
They dumped huge numbers of them on the Oz market------at their cheapest,you could pick up AM rigs at K-mart
for $40-$50.
CBers were everywhere--all over the (then) 11metre Ham band.
The poor old Novice licences were totally outnumbered.
The CB-ers whinged,& whinged until the Authorities threw in the towel & made CB legal.
There was a " sting in the tail",though---there were only 18 channels,including two "Oz only" ones.
You could still use the 23ch radios,but you only had 16 legal channels.
There was also Licensing & Callsigns.
Of course,most of the CB crowd ignored that,& whinged & moaned,until Licensing & Callsigns were dropped,& 40 channels were legalised on the FCC plan.
Now,all the law-abiding people who bought 18ch rigs lost two of the channels which became illegal.
The Govt's idea was to move all the CB activities to 40 channels on around 477MHz UHF FM by 1982.
The HF CBers wouldn't have a bar of it,at the time,so it was quietly forgotten.
Truckies started to use UHF to get away from "the morons on 27MHz",& when Repeaters became permissible,UHF CB began to get a following.
As the '80s & '90s wore on,27MHz withered away,until,by the turn of the Century,you would be lucky to hear anything ,whilst UHF did quite well for a while,although never with the shoals of stations of the early 27MHz days.
With the advent of cellphones,however,UHF CB lost popularity,until,now most City channels are left to foulmouthed louts---just like everybody left 27MHz to get away from!