Often1

I would be very surprised if you encounter any push back from AA. You are due a refund both under EC 261/2004 and US DOT rules.

AA's system is fairly automated and you will likely be able to both cancel and request a refund online. If not, this should be handled with a call (current hold times are fairly short and the US number is 24/7). While AA may try to get you to accept a credit rather than a refund, simply decline that and make it clear that you want a refund. Most are finding that refunds for unused tickets such as this are processed in 3-5 days and you will see the credit to your credit card as soon thereafter as your bank processes such items.

Should, for some reason AA either decline or not initiate the refund within 7 days, you may initiate a chargeback with your credit card issuer (bank) and file a DOT complaint. The advantage of the DOT process is that DOT will forward the complaint to AA with the requirement that AA respond to you with a copy to DOT. As you are legally entitled to a refund, the only response AA can issue is to advise that it has issued a refund.

Most are finding that the AA process is simple and automated. At worst, there is a bit of foot-dragging, but AA seems to have taken heed of the two warnings issued by DOT regarding its 2011 refund rules.

The 14-day notice issue is irrelevant to reimbursements (refund).