what does McCulloch v. Maryland have to do with supremacy clause?

The case centered on Article IV's National Supremacy Clause and the Necessary and Proper Clause, Article I, Section 8. Was the Bank of the United States a “necessary and proper” exercise of powers granted by the Constitution or was the bank unconstitutional? Did the National Supremacy Clause prohibit State taxes on federal activities or was the Maryland tax law constitutional? Was the Maryland tax on only federally chartered banks a discriminatory action, antagonistic to the federal system?

The Constitution was the instrument of the people, not the States. Therefore, the Court asserted the supremacy of the Federal Constitution over the States. The Court also emphasized the importance of national supremacy. Marshall stated that “…the Government of the Union, though limited in its powers, is supreme within its sphere of action….”

National Supremacy Clause

A state can't tax a federal institute because the National Gov't is supreme.

wrong section.