Taking a bite out Hawaii is a far cry from taking the continental US.
And as history demonstrated, America's power in retribution is formidable. That, without more (as long as it is recalled and credible), is a deterrent.
Which countries, in your mind, are credible threats to the 50 US states?
Mind you, I am all for a strong defense. And, as you appear to be a student of military, infantry is what it takes to hold a country. Not that I want a war on US soil, but what country in its right mind would mount a war against heavily armed and angry citizens?
I can't predict the future, but 10 years ago a group of people in Afghanistan planned and carried out an attack that resulted in the death of 2,900 Americans on American soil. After that happened, we didn't fight the attackers here in the United States. Instead, we took the fight to them in Afghanistan. And ultimately, we killed their leader in Pakistan earlier this year. If we didn't have troops overseas, it would have been pretty hard to do that stuff.
Not Obama's America; that is why he is desperate to disarm us!