I have the exact opposite experience. Amex USA is in bed with airline partners and if an airline refuses a refund, Amex will side with them and make no attempt to help. Even on cancelled flights, flexible & refundable ticket, Amex refused to help me. Twice even, when I reopened the dispute and repeated that there was no reason whatsoever I should not get my money back. They closed the case, period, and refused to give an explanation or address the arguments that I raised.

Conversely, smooth sailing with Chase, although not with the same airlines.