No. We are still a federation, we are NOT a unitary state. Yes, the federal govt has been trying to take powers away (because since the New Deal, the Democrats are very pro unitary state, pro big federal govt and they have inherited all of the “federalist” sentiments from the late 18th century.
We are still 100% a federation because everything not discussed in the constitution is the domain of the states. Some of the powers the federal govt has been given, the states can take a way if they decide to.
Also, the states can call a for a constitutional admendment without Congress and only the states can call for a Constitutional Convention.
So the true power does reside with the states. The federal govt can only “force” it’s social and domestic agenda by blackmail by witholding federal grants.
Point is, we are still a federation because the states the the LEGAL right and power to reign in the Federal govt even if the states choose not to do so.
But in a unitary state, the local govts have zero rights or legal power and the central govt can close those local govts if it wishes.