Check the aa.com web site for your PDX-ORD-GLA itinerary. If your connection doesn't appear it means that AA doesn't think it is a reliable conx. Even if there is a note "Short connecting time", I wouldn't risk it.
There are very few AA direct flights from PDX to ORD. Most PDX-ORD AA service I found involves a change at Seattle.
I wouldn't accept anything less than a one-hour connection - and I'd worry about that.