Article IV, Section 2, Clause 1

https://constitution.congress.gov/browse/essay/artIV-S2-C1-1/ALDE_00013777/

The first section of Article IV, Section 2 provides that the citizens of each state shall be entitled to all Privileges and Immunities of the citizens of other states. The provision is often called the Privileges and Immunities Clause or the Comity Clause. This Clause, which is textually tied to state citizenship, should not be confused with the distinct provision in the Fourteenth Amendment—the Privileges or Immunities Clause—which protects the privileges or immunities of citizens of the United States against state invasion.

Congress distinguishes between two types of citizens, citizens of each state and citizens of the United States. These are the political statuses that exist in the United States of America. You have citizens of the individual states, who have separate privileges and immunities from those of citizens of the United States.