• In the United States, a state is a constituent political entity, of which there are currently 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory and shares its sovereignty with the federal government. Due to this shared sovereignty, Americans are citizens both of the federal republic and of the state in which they reside.

• In Paul v. Virginia, 75 U.S. 168 (1869), the Court defined freedom of movement as "right of free ingress into other States, and egress from them."[1] However, the Supreme Court did not invest the federal government with the authority to protect freedom of movement. Under the "privileges and immunities" clause, this authority was given to the states.

• Federalism in the United States also referred to as the doctrine of shared sovereignty, is the constitutional division of power between U.S. state governments and the federal government of the United States.

It's complicated so no problem if it's not understood.