The Supremacy Clause in the U.S. Constitution asserts that federal laws and treaties take precedence over state laws. This clause is significant because it establishes a hierarchical framework for law, ensuring a unified legal system. It prevents states from enacting conflicting laws that could undermine federal authority and maintains the unity of the nation. This principle is crucial for upholding the Constitution as the highest legal document, promoting stability and consistency across the country and reinforcing the rule of law.