I've been accused of being too cynical, but my guess is that the brain trust at the DOT didn't realize that the HND operating restrictions applicable to flights to/from the lower 48 would make the use of HND a practical and financial impossibility. My cynical side further thinks the Japanese gov't did realize it. I understand that HND is a seriously busy airport, but there isn't a four or five runway airport in the world that can't squeeze in a mere FOUR daily landings and departures at any time of day the carriers think is optimal.
Further compounding the difficulty is the way that Japan, and Tokyo in particular, roll up some of the sidewalks late in the evening. The trains don't run all night, making for what I've heard is an extremely expensive cab ride to/from HND for arrivals and departures. Contrast that to SIN (where the subways don't run all night, just like Tokyo) which features extremely affordable taxi rates to the city.
AA's experience from JFK (along with DL's experience from DTW) ably demonstrate that the existing operating restrictions make HND non-viable from time zones other than the Pacific time zone.
Even worse, it's becoming apparent that there aren't actually bazillions of O&D business travelers for whom HND is a vastly superior gateway. Witness JL and NH basically duplicating their NRT hubs at HND, with flights to SIN, BKK, etc. All from an overcrowded airport that Japan tried to replace decades ago (with unimpressive results). Japan's refusal to forcefully evict the NRT-area farmers doomed NRT to expensive white-elephant status, with just a single runway until 2002, and still just one short and one long runway in 2014.
Open Skies - sure the US got Open Skies to Japan. No restrictions on KIX or NGO, and at NRT there are available slots for new service. HND is the exception.