This may well be part of the AA crackdown. It struck me that the sudden and mysterious approach smacked of one of Citi's bank regulators having raised the issue of dangling too many bonuses in front of people who had no economic need for another card. If that is the case, it would make all the sense in the world for Citi to crack down on its underwriting.

As noted above, it would do little good, in any event, to have Citi issue the card with the bonus, only to have AA credit the bonus and then close and zero out the account.

OP has not supplied any details, so not much to be said. Did he have another card and when?