Just as an outsider, I don't think de-hubbing an operation is the same as a "pull out" per se. I'm sure your mgmt would be aggressively selling tickets, just connecting through another regional hub.

AA can't fly international out of DCA, no one can.

If y'all haven't noticed, all the majors have been retrenching into their respective uncontested hubs (with exception of LA and ORD).

Revenue from IAD wouldn't go away, it would just be connect in EWR or JFK to go overseas or ORD or PHL etc. In general though gov tickets aren't all that profitable, it's the lobbyists and private companies doing business in the capital that would bring the profit on a direct flight.

If UAL de-hubbs LAX, they would probably be trying instead to funnel more traffic through SFO, IAH and DEN