Chuck Reti ) writes:

They had to scrap that callsign system as it did not
comply with ITU convention- US calls have to begin with W, K, N, AA-AL,
and not a number. This was an issue as someone apparently didn't
consider that propagation could carry CB signals across international
borders, so the ITU regs applied.

This is an understatement. If they'd given thought to propagation, they'd
not have allocated 27MHz to a band intended for local use.

Even with nobody working skip, when the skip was in the band got cluttered.
You couldn't avoid propagation getting those distant signals to you, and
that did not help the intended use of the band.

Michael VE2BVW