Renee ... I think that's doable, but it's going to be a little tight. An hour and eleven minutes isn't a great deal of time, and you'll have to transfer to another concourse for the SXM flight. I'd suggest the following. I wouldn't gate check any bags in Pittsburgh because you may have to wait for them when you depart in Philly. Make sure your carry-on stays with you. Assume that any checked bags you have won't make the connecting flight. So, in your carry-on bring the essentials you'll need for one full day on the island (such as a change of clothes). I'm not saying this will happen, but if I had to wager money on what airport would mess this up the smart money would be on Philly. One time they lost my suitcase there for entire week. If you can, tell me what concourse gate you'll be landing at, and which one you will be departing from. I may be able to share some advice here such as whether it's smart to take the shuttle bus or just walk. Also, not worth switching to Charlotte now for just a 59 minute layover.

Overall, I think you'll be fine. As for AA, my opinion is just my opinion but I honestly believe they could care less about who they inconvenience. Next to the true budget airlines like Frontier or Spirit, they will always be the last airline I choose if and when all other options have been exhausted.