Travel consultant said that NH is indeed obligated to provide transportation in the class of service booked, whether an award ticket or not. He figures it may take NH 48 hours or so to re-accommodate everyone in their week-long batch list of newly cancelled flights. US would then re-issue the ticket.

Will be interesting to see what route is chosen/suggested; presumably SFO-NRT is default but there is more revenue space on LAX-HND.