One ex-RAAF B.20 A84-229 did go to the USA in the 1980s. It was operated by a Yank called Steve someone, registered N229CA. I believe that he subsequently sold it, doubt that it is still airworthy.
Steve Picatti....... and yes it appears to have been sold to Jack Stringer at Palo Alto, Ca around 1997, but it's current status is unknown, so, as you say very likely it's not flown for maybe 10 years or more....?
It would also appear that the two ex-RAE Canberra's (XH567 & WT327) that were being operated in the USA by Air Platforms Inc on high altitude research work may also now no longer be airworthy, as Air Platforms Inc is now a dissolved corporation, so status unknown should be applied to these two airframes now as well.
That's maybe then the source of where Air Altlantique Classic flight have acquired a spare engine from for WK163...?
So, with the Coventry and Temora examples currently un-airworthy and unknown status for the other known civvie examples, it would seem only the two much modified NASA RB-57's are the only active examples of the breed.