Here's the thing tho...Hawaii was important; back when ships ran on sail and/or coal, before planes could fly non stop round the world, before labor laws and unions and the constitution put an end to profitable agriculture.
Nowadays, we have tourism and Inouye, pretty much the only reasons why anyone has stuck around, including the military.
Hawaii has no resources, therefore it will not be invaded, ever.
Hawaii produces nothing worthwhile to justify invasion.
Hawaii is not targeted by any countries ICBMs.
Even terrorist could care less about Hawaii.
On topic, the best way I see to stop/resist an invasion would be, to not write letters, but to form community militias now.