They author is correct.
You said that the amendment destroyed the last vestige of federalism,
It did.
but federalism refers to the power being at the federal government level.
Federalism doesn't mean any such thing.
Federalism: A form of political organization in which governmental power is divided between a central government and territorial subdivisions--in the United States, among the national, state, and local governments.
L
But, if federalism refers to the states having more say and sharing power with the federal government, then what is the opposite? I thought the big argument was between states’ rights vs. federalism? (Again, I’m not arguing; I just want to learn. It sounds like the opposite of what I thought.)