Only people who are not U.S. citizens need special permission to enter U.S. territory.
When you get your U.S. passport in the mail, it comes with a flyer that says "With your U.S. passport, the World is Yours!" Holders of the U.S. passport are accustomed to simply arriving at the border of another country, showing their passport, and easily crossing in. Rarely, they have to apply beforehand for a visa. If they pay the fee and fill out the application correctly, the visa is routinely granted. Holders of a U.S. passport tend to believe that freedom to travel is their birthright, a view reinforced by the literature that comes with their passport. For the cost of a plane ticket, they can leave the country they were born in any time they want.