On a related note, I had a US based Delta AMEX before moving my address to overseas.
I kept the card and I occasionally charge small amounts to it.
Never got any mileage credit after the address move.
On a single occasion I had a few 10's of miles credited, only to see it reversed a few days later. Rather strange, since the reversal came in the form of three different negative mileage that almost add to the credited total, but not quite.
For the record, the purchase originating the credit was for wifi on board a Delta flight.