What did hawaii have to do with us plans involving asia?

Well, Hawaii is closer to Asia, so it is something like a resting point. The US can stop there, hold a base perhaps, and then go to Asia from a closer point. Like with WWII and island hopping. Or it's probably talking about how the island helps with trade and being closer. Not entirely sure what you're looking for, but hope this helps.

4.a depression is the answer