Calvin Ellis, Kryptonian name Kalel, also known as Superman, is a Kryptonian president of the United States, on a different Earth in the Multiverse. On his Earth, he became Superman in addition to being the president. It is likely he's native to Vathlo Island, due to his reference to the word Vathlo.
During Final Crisis, this Superman joined a a team of different versions of Superman from the Multiverse. ("Final Crisis")
New 52 Continuity
Born to Jorel and Lara in the science capital on Vathlo Island on Krypton, baby Kalel was sent to Earth to escape Krypton's destruction. He was found and raised by a human couple. As an adult, he operated as Superman while also serving as the President of the United States.
One day, inhabitants from an alternate Earth came through to his Earth, fleeing from their universe's Superman, who they had created. When the evil Superman came through, Superman fought him and won, with the help of Lex Luthor. ("The Curse of Superman")
Superman also interferes directly in his country's international affairs, using his powers as Superman. Shortly after the encounter with the alternate Superman, he destroyed all of Bialya's nuclear facilities, and then invited them to join the international community. ("Executive Power")
Behind the Scenes
Calvin Ellis is based on real-life President Barack Obama.
The character was unnamed in his first appearance in Final Crisis, and so was assumed to simply be Barack Obama. However, with the release of Action Comics #9, his name was revealed to be Calvin Ellis. He also had the Kryptonian name of Kalel.
There was previously another black Superman in Legends of the DC Universe: Crisis on Infinite Earths (Feb. 1999). This version lives on Earth-D, which featured a more ethnically diverse version of several Earth-One heroes, such as an Asian Flash and an American Indian Green Arrow. The Earth-D heroes had never experienced major tragedies in their lives. It was a combination of modern multi-cultural sensibilities combined with Silver-Age-style innocence.