doesn't matter what data you pull, it won't change the result. DL and UA aren't going to enter the market based on the size of the market. They will enter the market based on their ability to profitably serve it.
A 787 won't fix what ails AA in LAX-Asia.
DOT data shows that DL's revenue on LAX-HND - the weaker of its two LAX-Tokyo routes exceeds revenue on AA's LAX-NRT route by 50%. Further, DL's HND flights are flown on 767s while AA's NRT flights are flown on 777s which weigh and burn almost 50% more.
And both of AA's LAX-Asia flights combined generate just over the revenue on DL's LAX-NRT alone.
So either you might want to rethink your notion about how badly Japan is doing for DL or you might explain why AA's Asian operations are not solidly in the black. Apparently they were telling the truth when they said that NRT was their highest margin hub just a few months ago - which also pretty well makes it clear that DL is restructuring its Asian operations from a position of strength and profitability and not desperation and losses.
Since DL reported its Pacific operations as a whole had a 24% operating margin, just under the 25% for Atlantic operations, the NRT hub alone had to be higher than either of those numbers.
A 787 isn't going to cut trip costs by 50%.