It seems quite obvious to me that many people understand the dynamics (again, some might use that pesky word "reality") of NRT better than you, and have for quite some time.
While you've been doing the Baghdad Bob routine - for years, indeed - assuring everyone that NRT was perfectly fine, Delta has continued reducing capacity there, with smaller planes and fewer flights. And once again, lest anyone forget, contrary to your latest attempt at finding a cogent argument, this long predates the recent Yen devaluation, and is actually a continuation of the long-term trend that began years before Delta and Northwest even merged. NRT is simply no longer competitive as a hub for Asia for any U.S. airline, which is why we've seen both U.S. airlines with hubs there progressively dismantle said hubs. United just accomplished this faster because it had so much better a U.S. hub structure to work with.
With respect to the latest diversion about the local U.S.-Japan market, Delta will, indeed, being offering about 37% more capacity between the U.S. and Japan next year than United by my count (based on present schedules). Although, unlike United, which will dedicate 12% of said capacity to Hawaii, over 28% of Delta's U.S.-Japan capacity will be between HNL and NRT/KIX/NGO/FUK. And once again, if Delta wants to be the airline of choice for vacationers flying between Japan and Hawaii, it's obvious other carriers aren't all that interested in fighting them for that traffic. When you exclude the Hawaii beach traffic and look at the Mainland U.S.-Japan market, the gap in capacity between Delta and United falls to just 10%, which is perfectly fine for United considering it's far stronger non-Japan Asia network. And all of this is rather academic anyway since sheer capacity is far less important that network access, and United's hubs are so far superior to anything Delta (or AA) has when it comes to Asia, that I'm sure United will be just fine.
Once again - this is precisely why Delta is behaving the way they are in SEA: Delta is falling further and further behind United when it comes to Asia and the most critical step in addressing this deficiency is replacing NRT with SEA as the key gateway across the Pacific.