Both SEA and PHL are in the US, thus no immigration ! OP simply walks off his inbound flight and to his departure gate. No Flight Connections, security checkpoint or other checks. Depending on his exact arrival gate, the walk may be between 5-20 minutes.

If the connection is sold by AA, it is within MCT and thus "legal".

Nonetheless, you know your own preferences and abilities. Just because a connection is within MCT, does not make it within SCT (Sensible Connection Time). If you require or prefer more time to make it from gate to gate, then do not book a short connection. Bear in mind that AA requires you to be at the departure gate for DUB no later than 30 minutes prior to scheduled departure. While you will not generally be off-loaded if not present, if the flight if overbooked and at risk of oversale, AA may offload you in order to avoid the oversale, if you are late.

As others note, the baggage app is helpful. It shows you what the agents see on their screeen and your bag is scanned at every movement. Thus, off the inbound flight from SEA and onto the aircraft to DUB. But, don't obsess about your luggage as there is nothing to be done about it anyway. AA ramp personnel know exactly which bags are missing and make the calculations to close the baggage holds based on that if possible.