Most are done more efficiently on a nation-wide basis, but fine, have the states do them.
It'll cost more and it still requires tax revenue.
It has not been shown that "many" are done more efficiently on a nationwide basis. Many can and should be done by the states according to our national constitution. And I like the idea of letting the states decide whether they really need to be done or not. If the states decide that they are not cost effective, it will save us a lot.
We used to get along just fine with a lot less federal interference.
The feds should be only concerned with protecting the citizens of this country and enemies foreign and domestic. They also have some responsibility in the area of coordinating some of the infrastructure. They also are responsible for treating with foreign entities.
But the states can and should handle most of the rest. That was the intent of the founding fathers. The constitution was written to protect the individual citizens and the states from a centralized government overstepping it's authorized powers.