Still not strictly AAs fault, but at the beginning of the plague years AA ditched their 757s, 767s, and A330s expecting a much longer multi-year drop in demand. AA expected to replace them with 787s. United parked their planes but didn't sell them off. United now has capacity to add flights, and will have more once they are able to bring their P&W 777-200s back online after engine mods (reinforced cowling, increased inspection frequency). If Boeing could deliver faster, AA could recover better, but there still was a bit of miscalculation on AA's part.
Edited: according to this article on Live and Let's Fly (https://liveandletsfly.com/american-airlines-boeing-787/), AA still has their 757s, 767s, and A330s, parked. AA is even still leasing some of them. They could bring them back in service, and with some re-jiggering of schedules and aircraft make many of those routes work. But (again according to the article) Boeing is writing them a check.