A FlyerTalk Posting Legend
Join Date: Jul 2002
Location: MCI
Programs: AA Gold 1MM, AS MVP, UA Silver, WN A-List, Marriott LT Titanium, HH Diamond
Posts: 52,575
AA isn't going to give the OP a free change on the outbound...only the return. (I'm assuming that only the return was auto-rebooked.)
Especially on a peak travel day. Honestly, the best defense against having this whole thing going pear-shaped is being in NYC early enough that day to react if LGA is having WX/ATC issues - either with an earlier flight or a train to Philly. (Obviously you'd need to be "officially" delayed and communicate with AA before you took a train to Philly...)