Your friend is partially right and wrong. Benjamin Franklin was not a president of the United States of America. But, he was the 6th President of Pennsylvania.
He is the President of Pennsylvania because the Government of the Commonwealth of Pennsylvania has three branches just like the United States of America. It has an executive, legislative, and judicial branch.
Benjamin Franklin was the President of Pennsylvania. He was the head of the executive branch of the State Government of Pennsylvania and serves as the commander-in-chief of the state's military force.
The term President of Pennsylvania is now popularly known as the Governor of the Commonwealth of Pennsylvania.