Just experienced something similar:
1) Jan 2025: Booked an AA biz (U) with 35K miles, 1 transcon connecting to 1 short haul both in U.
2) Never got any updates about schedule changes etc. I just happened to check on my itinerary on AS, and saw the transcon U disappeared, with a message asking me to call AS.
3) July 2025: AS agent (US-based) said AA cancelled the transcon flight, and my only option is to cancel and get my miles back. The other "option" is to rebook into a direct transcon in coach with "no penalty", even though I could have booked the same for 25K miles. I did point out I paid 35K for a biz itinerary, but she stated "the computer would not let her rebook" without repricing the whole thing.

I was able to get a comparable transcon biz flight in AA for 40K miles.

My main gripe is AS made no effort to notify me about the schedule change. Imagine my surprise if I had waited until the day/week of travel, just to realize I don't actually have a flight and likely have to pay even more in money or miles.
Lesson learned for me is to watch over AA award flights booked with AS miles, especially when booking far out in advance.