Why do U. S. states have their own constitutions?

Each state is allowed to run itself. They make their own rules and have their own mayors.

Answer:The u. s. states have their own constitutions the country is divided into states and the Constitution allows states many powers. Each state then has to run itself and each state has the power to write its own state constitution. The 50 states each then had to design and create their own state government the state constitutions do exactly that.