This would not applied to the OP, but for future reference, you are traveling XXX-HNL-GUM, there are options to go through NRT if flight to HNL is delayed or canceled. For example, from LAX, the flights to HNL all leave no later than 10:00 am. Flights to Tokyo leave around noon, so I’ve bailed on HNL and picked up LAX-NRT-GUM several times over the years.
Similar flights to NRT are available ex SFO, DEN, etc.