Current AA hubbing policies making decent maximised xONEx's difficult.

eg. Due to the transcon resrictions on an xONE I would think it would be reasonably common to try and fly (for example)
DFW/ORD - NYC (city) - LAX

However available flights as follows mean there is only a few single pairs of flights that work (examples for Aug-10 schedules from ExpertFlyer), otherwise you have to burn a segment on a city airport transfer.

DFW-NYC
1 to JFK (AA400 1050-1530), 15 to LGA, 6 to EWR
ORD-NYC
1 to JFK (AA1362 1135-1459), 15 to LGA, 8 to EWR
NYC-LAX
10 from JFK, 1 from EWR (AA119 1850-2155 (2class 738)), 0 from

Is AA only using JFK for long haul and LGA/EWR for short ??

I often fly the route you describe. And at least there is a daily service to JFK from ORD/DFW so you usually are able to make it. But yes, it requires some extra time as there isn't much choice. IIRC there used to be more flights but they are all gone.
AA also has some longer routes from LGA this year going to Santa Ana for example.
Those AA flights to JFK are partly designed for people to make connections at JFK and not really with a xONEx in mind. And not many people at DFW/ORD need to make a connection at JFK.

La Guardia, like Washington National (DCA) labors under "perimeter rules" that limit outbound flight distances. These are holdovers from when Idlewild and Dulles were emerging as the long-distance airports for NYC and DC, and are mainly politically-enforced.

Long-appearing segments like LGA-SNA usually, upon closer examination, entail a stop in DFW or some such; the flight number doesn't change despite there being two sectors to the segment.

LGA is a critical O/D market as it's usually easier and quicker to get into Manhattan compared to JFK; in the case of DCA the airport's close enough to the District that it presents noise pollution issues around the Capitol and White House.

But I have only two words regarding xONEx-unfriendly hubbing policies. Gat. Wick.

And two more: ex-UK

Another very good reason for praying that JetBlue joins OneWorld.....

Or their biggest shareholder pushes them towards *A. Actually, I think they will just stay where they are.