The constitution doesn't mention health care at all. This doesn't make dealing with health care unconstitutional. Something is unconstitutional if it is done in violation of the constitution. Plenty of legal things in the US are done by government that are not mentioned in the constitution.
Regarding the Economics textbook I refer you to:
en.wikipedia.org/wiki/2008_United_States_federal_budget
In particular note that by calling wars "Special Appropriations" their cost is not listed in the budget entirely. With special appropriations actually included military spending skyrockets.
Even without the special appropriations the following is a breakdown of expenses related to the military:
1. 481.4 Billion in DoD non appropriated spending
2. 145.2 Billion in War on Terror non appropriated spending
3. 39.4 Billion for Veterans Affairs
4. 34.3 Billion for Homeland Security
Social Security costs:
608 Billion which is more than paid for by Social Security Deductions (927.2 Billion).
386 Billion is spent on Medicare
209 Billion on Medicaid and SCHIP.
324 Billion on all Welfare, EI and other such programs.
The total is approximately 1.5 Trillion (as interest in national debt is not social security and shouldn't be included in this line item).
In comparison the government debt at the end of 2007 is 5.04 trillion en.wikipedia.org/wiki/2007_United_States_federal_budget
While the projected government debt at the end of 2008 is 10.8 trillion. As the deficit of declared items was approximately 240 billion dollars or approximately 0.25 trillion (rounded up for convenience), the total special appropriations is:
10.8 -0.25 -5.04 = 5.51 Trillion Dollars. A number which radically dwarfs
social security spending. The vast majority of this are the Iraq and Afghanistan wars.
There is a point to be made that the entirety of federal level social programs is not as insignificant as I claimed, but trying to argue that military spending is only 4% of actual spending is rather erroneous.