Yes, and congress could pass a law banning net neutrality. But under current law, the FCC is not able to issue a directive doing the same thing.

A law banning NN will never get passed due to gridlock (thankfully), so barring some huge change in public opinion I don't see states being prohibited from enforcing NN.

Something being interstate commerce does not prevent states from legislating on it. Under that logic, states couldn't regulate the sale of anything produced in another state, which is obviously untrue.