My "plain white sticker" in an expired passport continues to be accepted too, as it should be. I'll use it again in a few weeks in conjunction with a current passport.

Now here is an interesting situation indicated on the Argentine consulate website above: Argentina-US dual-citizen flying to Argentina on a US passport with an Argentine birth certificate need not pay the reciprocity fee to travel to Argentina; and they get processed as an Argentine on arrival.

What happens on arrival at EZE if the US citizen who flies to Argentina on a US passport with an Argentine birth certificate is not a dual-citizen? [Say the person happened to be born in Argentina to a couple of diplomats assigned to Argentina at the time of birth of this US citizen.]