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.
For most of the world's population, though, freedom to travel is a distant dream. They can't leave the country of their birth because instead of that magical ownership of the world that comes with a U.S. passport, they are citizens of countries in Africa, Latin America, or most of Asia. Many of them are also poor, and people of color.