Put this into perspective, once the US finished paying interest on debt, medicare and welfare there's no money left over for anything else.
Science programs are one thing, but the government can't deliver 70 year old services with reasonable efficiency.
Most federal welfare programs, however, involve cutting a check. Look at the Social Security Administration. It has a budget of about $12.7 billion, and administers $700-800 billion in benefits to 50-60 million people: http://www.ssa.gov/pressoffice/basicfact.htm
That amounts to an overhead of 1.6%, or ~$250 per person served.
Or, look at it another way. Total federal payroll is about $180 billion, for 2.15 million federal employees (a number that has fluctuated between 1.8 and 2.2 million for the last half century despite nearly a doubling of the population). That's about 4.7% of the budget, or 1.2% of GDP.
Most of the federal government is not overhead. 95% of it is just taking in tax revenue from certain people and cutting checks to other people.