The dictionary label of "chiefly North American" or similar is borne out by the News on the Web corpus, where it seems
kibitz and its related words are used about eight times as frequently in the US and Canada as they are in the UK. The words are not completely absent from British publications, as for instance in the
Guardian in July 2017:
Seven times in the last eight years the second Friday of Wimbledon has been an all-out Murray gig, with TV schedules cleared and the hill at the back of No1 Court loaded with flag-wavers, jug-quaffers, kibitzers, day-trippers, ruddy-faced once-a-year tennis ultras.
(Incidentally, my spell-checker queries
jug-quaffers, but not
kibitzers.)
Whether these words would qualify as common in the context of North American English is a question I don't need to answer. I'm satisfied they're not common across the whole Chi world.
This family of words are rare, by our criteria, so I will change the status of
kibitz,
kibitzes,
kibitzed,
kibitzing and
kibitzer.