With regards to your first paragraph, we have plenty of money to spend on defense. The USA is expected to spend around 1.2 trillion dollars on defense in 2014 [0]. The problem, is that most of that spending is overseas "defense", and very little of it is used to secure critical domestic infrastructure. Like our energy grids, our roads and highways, etc.
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[0]: https://en.wikipedia.org/wiki/Military_budget_of_the_United_...