This is sad ...
The USA military expenditure, according to 2005 figures is US$ 548,531,000,000 per year.
This is almost 6 times more than the second largest military spender (China).
A simple calculation shows that the US can cut their defense spending by half, and still be at 3 times more than China.
This could balance their budget over the years too, and perhaps cause economic growth as well, while keeping them as the best defended country in the world.
The irony here is that for the USA to economically grow they need to balance the budget, rather than pile on deficits year after year. This is in their long term interest, and ensures they remain a world power. If they don't do that, they risk ceasing to be a world power, and would be like present day Britain for example.
But it makes too much sense, so it is not going to happen.
Detailed data here: List of countries by military expenditures.