The 'genius' who rebooked you was likely a bot that just looked at the nearest flight on the leg that got cancelled. It would have caught up with the mis match with your connection from Florence at some point. This is pretty standard practice and it usually comes out in the wash.
Rather then beef about that you need to be proactive and research reasonable, alternative routings that work for you and put those to AA.
That might inlude e,g, MAD-DFW/JFK (or other AA hub) and connect to LAX from there or perhaps BA to LHR then AA to LAX.
AA can't force partners to open up reward seats but they can open up rewards on their own metal.
But basically your rights uner EU261 are
- re-routing to the same destination at the earliest opportunity (under comparable conditions);
- later rerouting, at the passenger's convenience, to the same destination under comparable conditions (subject to seat availability); or
- a refund of the ticket as well as a return flight to the point of first departure, when relevant.