Have you tried the multi-city booking on aa.com? (
https://www.aa.com/booking/find-flights)
I tried it with a dummy JFK-NRT(stopover 3 days)-HKG(stopover 2 days)-NRT(stopover 2 days)-DFW-JFK itinenary couple days ago, the price is pretty close to what a JFK-NRT or JFK-ORD-HKG would cost.