Diners Club cards issued in USA and Canada are Mastercards. Diners Club cards issued anywhere else are not, but will be accepted by Mastercard merchants in USA and Canada only. In other words, a Diners Club card issued in The Netherlands would be accepted by Mastercard merchants in the USA and Canada, but only by Diners Club merchants elsewhere.
Do you really need to earn AAdvantage miles rather than miles in another OneWorld program which can be redeemed for travel on AA?
I'm a member of AAdvantage, but I'm interested in other opportunities also. For example: I know Diners Club in NL has a cobranded card with BA, but unfortunately -as I already mentioned- it's rare that a merchant accept Diners Club, so it's not really an option.
My best guesses are for Visa and/or Mastercard.