15.9% probably greatly overestimates the extent of the American welfare state - notice the number for Canada is just 0.6% higher. Consider the grossly inefficient American health care system. Because of lack of cost controls on medical procedures and equipment, Medicare and Medicaid spending is vastly inflated despite the fact that neither is a universal system.
I suspect the inefficiency and redundancy of much U.S. government spending (caused in part by our constitutional division of labor between local, state, and federal authorities), along with the military budget, causes a higher figure for government spending in the U.S. than is warranted by the level of public services. This in turn, engenders a belief in the lack of efficiency of government and antagonism towards paying taxes.