Okay. I try to explain step-by-step.
1, Go aa.com and "Make Reservation" -> "More Option"
2, Using "Round Trip" option,
From: SEA To: PUJ
Search By: Fare
Departure Date: Nov 8 All Day, Return Date: Nov 16 All Day
First/Premium: With Restrictions
Choose a Carrier: All Carriers
3, Click "GO"
US fares are there!