Article II, Section 2 of the U.S. Constitution states as follows:
The President…shall have the power to grant reprieves and pardons for offenses against the United States.
As I said, the President’s power of pardon only applies to offenses against the United States as a whole not to offenses against an individual state or locality.
The phrase "offenses against the United States" means federal crimes, as opposed to offenses against the several states.
At the time the Constitution was adopted, the "United States" was a plural noun. It took Lincoln and the Civil War to convert it to a singular noun. With many good effects and some bad effects.