If I have an SSN (from working at a student in the US many years ago), a US bank account and an address at which to receive correspondence, can I legitimately get an Citi Platinum

If I have an SSN (from working at a student in the US many years ago), a US bank account and an address at which to receive correspondence, can I legitimately get an Citi Platinum AAdvantage card even though I live here and have no US citizenship?

Otherwise, is there an Australian card with both zero foreign transaction fees, and meaningful (not FlyBuys) rewards points in a useful airline program? Velocity or AAdvantage would be ideal.

You seem to have much of what would be required for a U.S. card.  SSN's do not expire. But, one hurdle may be a driver license - these are sometimes required as secondary I.D. Another may very well be a U.S. credit rating - without that it could be very difficult. Give it a try, you certainly don't need to be a U.S. citizen to get a credit card there, unless that is made a condition for a particular card offer.

There certainly will be a question about U.S. Citizenship/Permanent Resident (but as per U.S Law, they cannot cross check this). SSN is all you need along with a verifiable PO Box or other address (their banks are not that strict!).

However, with no credit history, the biggest issue you would have is the credit limit you may get. This can be as low as $1500 and can be improved every 6 months. No credit history does not mean you won't get a credit card, you just won't get a high end credit card. Any of the Zero annual fee cards will suffice.

Without a sound credit history you are unlikely to get City Plat. 

You can check your credit rating at credit.com and look at cc offers available to you at creditkarma.com

I am not aware of any AAdvantage card in Australia but there are plenty of Velocity links on this site (ayes the.com.au)