Federal Constitution vs. State Constitution

The following questions should be answered within the essay. Could a country such as the United States function without a federal constitution? Would it be possible for each state to merely abide by its own constitution? Why shouldn’t the US Constitution include an overall criminal code specifying crimes and punishments that could apply [universally] throughout the US? Can you think of current tensions between states’ rights and the federal government (e.g., gun laws, physician assisted suicide, legalization of marijuana, etc.) Discuss.