TL; DR: family of 4 with confirmed FCO-MAD-ORD-XXX itinerary booked and paid for via AA.com not allowed to check in as seats not rebooked by AA agent on codeshare partner (Iberia) at some point, resulting in $200-250 in expenses and >24h delay in arrival at final destination. Compensation due? How to get it?

I'm looking for advice regarding compensation due related to a recent misadventure with AA.

Last week we were booked to fly FCO-MAD-ORD-XXX. Upon arrival to FCO at 5 AM for our 7:45AM flight we went to checkin. The initial leg was on Iberia so we went to the Iberia desk to checkin. After a 30-45 minute wait in line the agent at the desk stated that our tickets had been changed and we no longer had seats on the FCO-MAD flight. She also stated there was nothing she could do to help and referred us to the AA desk. We went to the AA desk only to find they did not open until 8AM.

I called the AA reservation/ticket line at 1-800-433-7300. By now it is 5:45AM. After a 10 minute hold I reach an agent who starts to work on the situation.
Around 6:30-6:45 the agent tells us she thinks she can get us on the Iberia flight. I pointed out the time to departure and the fact that we would have to clear the Iberia line (still 30-45 minutes long), security, and immigration in an hour. She didn't think that was possible.

Over the course of the next 2 hours on hold she tells me that what happened is at some point there was a schedule change and an AA agent was supposed to rebook our Iberia flight but didn't. Unfortunately this all coincided with the winter storm last week and there were very few options for rebooking. We were ultimately rebooked on FCO-MUC-PHL-XXX, leaving at 6:50PM, requiring an overnight stay in MUC and getting us to our destination ~24h after originally scheduled. The agent told me that was our only other option was to return on January 11.

We were not offered any compensation for the delay or any assistance in the form of meals, accommodation or transportation. I did not ask while on the phone with the AA agent because I was exhausted by the early hour and the long hold times and distracted by my children. I realize I probably should have. The delay incurred ~200-250 in additional expenses in the form of food, transportation and the cost of a hotel room for 4 in Munich.

All flights were booked on AA.com and paid for with cash as a single itinerary approximately 9 months ago.
In August our outgoing flight was changed from XXX-ORD-MAD-FCO to XXX-PHL-FCO due to a broken connection in MAD after a schedule change. The return leg was not affected.
The entire itinerary was confirmed in September and in fact this leg had not changed since booking in March.

I believe this is an involuntarily denied boarding situation and should be covered by EC261 resulting in compensation of 600 eu pp as well as expenses incurred as our itinerary was >3500km and the delay was >4h. I have contacted AA customer service through their web form but have not received any response after ~60 hours. The catch is that we were never even allowed to check in and never made it to the gate despite presenting ourselves ~3h prior to scheduled departure.

Is that a reasonable interpretation?
Has anyone had a similar experience?
What was the outcome?
Is there a better way to contact AA to get a response?