The COTUS doesn't tell us which roads to build and where. It doesn't tell us what Pentagon programs are worth spending billions on. It doesn't tell us which wars to fight. It simply gives us the framework within which to make those decisions.
The Constitution gives Congress the power to collect taxes and provide for the "general welfare". That language is so broad that Congress essentially has free rein. It could certainly be argued that PBS provides for the general welfare by providing education and appreciation of our nation to its citizens.