The statement that best assesses the impact of the cases Marbury v. Madison and McCulloch v. Maryland on the Constitution is: "These cases established the principle of judicial review and affirmed the supremacy of federal law over state law."
Marbury v. Madison (1803) is pivotal because it established the principle of judicial review, allowing the Supreme Court to declare a law unconstitutional. This significantly strengthened the role of the judiciary within the balance of powers in the U.S. government.
McCulloch v. Maryland (1819) reinforced the supremacy of federal law over state law and the constitutionality of implied powers. It held that the federal government had implied powers under the Necessary and Proper Clause, and states could not impede legitimate federal actions, like the establishment of a national bank. Together, these decisions profoundly shaped the interpretation and application of the U.S. Constitution.