If the federal government were constitutional:
-There would be no social security
-There would be no medicare of federal medicaid, and also the requirement of medicaid for states to pay a certain percent is grossly unconstitutional.
-No federal nutrition guidelines
-No income taxes* 
-No federal police groping old ladies at the airport
-No ethanol subsidies or other subsidies of any kind. 
-No direct transfer payments to individuals via “tax credits”
-No graduated income tax rates 
-No preference for minorities over whites (Violates 14th amendment and no bill of attainder clause)
Which other of the myriad things it does are not constitutional that you can think of?
1: The government is technically given the power to have an income tax by the 16th amendment, which in and of itself was dubiously passed, however, it DID NOT make it legal for the government to be able to require you to investigate you to find out your income (or search for it), which is prohibited by the 4th amendment, and the 5th amendment prohibits them from forcing you to incriminate yourself, so as the constitution stands, the government can require you to pay income taxes, so long as you willingly surrender them to the government. (If the 16th amendment is even legitimate, evidence strongly suggests that it was not legitimately passed.)
2: The constitution does not grant this power, it grants the right to REGULATE interstate “commerce”, which by definition does not grant the right to make transfer payments, and if it did, you’d be required to cross a state line before receiving a subsidy… and that is just plain silly and obviously not the intent of the constitution.
3: Passing taxes only on certain groups of people is a bill of attainder because it targets one group in order to punish them more severely than it does others.