Here's American's published stroller policy:
Strollers
Each ticketed customer is allowed 1 stroller. Only small, collapsible and light strollers (up to 20lbs/9kgs) can be checked at the gate. Any stroller that weighs over 20lbs/9 kgs, is too large or is non−collapsible must be checked at the ticket counter.
Customers are allowed 1 stroller and 1 car seat per ticketed passenger. Both items may be checked at the ticket counter or one item can be checked at the gate and one at the counter. These items are checked at no charge, when traveling with a child or to adopt.
https://www.aa.com/i18n/travel-info/...g-children.jsp