i believe that there needs to be some sort of ready reserve national guard to defend any islands that are potential war targets. A lot of a countries that invaded us back then had difficulty managing wrest control over all our islands and we should be just switching ourselves to guerilla warfare at that point. in combination with the recent trends in warfare like drones for recon and even attacking the enemy at the rear we can manage with that. But dont forget, another advantage is that we're basically surrounded by seas so investing in the navy should be the priority first and foremost.