This is an extreme lower bound looking only at FICA. In reality you have:
-FICA
-State income tax
-Local taxes for your city
-Social security and medicare tax
-Sales tax at point of purchase
-Property taxes (directly if you own a home, indirectly + margin if you rent)
-Gas tax
-Vehicle registration fees/taxes when purchasing
-The payroll taxes your employer pays for paying you, directly suppressing your income/earning potential.
-A whole host of taxes on any capital gains, inheritance, gifts, your phone bill, the list goes on and on.
When you _only_ look at your tax burden in terms of what gets deducted from your check you get a highly misleading figure. This doesn't even factor in what happens when the gov inflates the currency and "taxes" your cash holdings.
Disintermediating the health care system with a public option could lead to the biggest savings in the system overall. The military budget stuff is somewhat disingenuous because it was necessary for the U.S. to maintain a capable military first because of the Soviet threat and later to back the USD as the global reserve currency and secure foreign oil - unless we could get the domestic shale up and running (USD as the reserve currency improves the purchasing power of every American and allows us to live "beyond our means" on an international level - while on the downside making our exports uncompetitive). But nevertheless, if our military went away, Americans would have to take a haircut to their standard of living.
So it's not as simple as you make it sound.