I have a major hearing impairment (though I am not to the level of profoundly deaf) and most of the time can't make out much of any announcement over the speakers in either the plane or the terminal unless it is relatively quiet and I'm lucky. It is stressful, especially if a flight is delayed. Are they moving us to a new gate? Is there a further delay? A change of equipment that necessitates new seat assignments? Did they just switch our bag assignments to a different carousel? It is stressful, though there are times when I'm thankful I can turn down my hearing aids and shut off a lot of the noise. I wish there was a subtitling mechanism at airports and on planes.
I don't think your situation quite rises to a violation of the ACA, though it wasn't a great example of proactive service on AA's part.
Is your lip-reading good? I can often get a seatmate to tell me what was just said and have a better chance of understanding because I can see his/her face. So far, that works.
Best of luck in your future travels. Honestly, I think this situation could just as easily arisen on any of the carriers. Deafness is a disability that people can't see and find it easy to forget even after they've been told. (I don't mean that in a negative way -- it is genuinely hard to remember for most people who are hearing. God save me from clients who routinely put their hands in front of their mouths when they speak.)