The biggest change in federalism in the U. S. since the civil war?

Federalism has evolved over the course of American history. At different points in time, the balance and boundaries between the national and state government have changed substantially. In the twentieth century, the role of the national government expanded dramatically, and it continues to expand in the twenty-first century

Explanation:

Dual Federalism (1789–1945)

Dual Federalism describes the nature of federalism for the first 150 years of the American republic, roughly 1789 through World War II. The Constitution outlined provisions for two types of government in the United States, national and state. For the most part, the national government dealt with national defense, foreign policy, and fostering commerce, whereas the states dealt with local matters, economic regulation, and criminal law. This type of federalism is also called Layer-Cake Federalism because, like a layer cake, the states’ and the national governments each had their own distinct areas of responsibility, and the different levels rarely overlapped.