It would probably be better to link Tax Increases to the Economic downturn, rather than relating it to military spending. Yes, the US spends a lot of money on the military, but once your military is that big, cutting can become a problem.
As demonstrated in the earlier posted graph, only a small part of the budget is on R&D - the majority is towards maintaining what the currently have. By cutting the spending, they'd either have to slow technological advancements, or shrink the size of the military.
The latter would result in a military equipment not really doing anything, and some angry people if you try and lay-off those who work in the military.
As for Government spending in general - few countries are in a surplus, let alone large economies. Going from a deficit to a surplus is by no means an easy task, especially when you consider the size of the deficits. Tax increases are a start, but by no means enough to resolve the situation. No, a lot of [proverbial] blood will be shed if we want to go back into a surplus, and doing so would jeopardise the country's economy as a whole.