Who was the first African American?

That all depends on how you wish to define the term "African American". Remember there were no African Americans until the 1980s when Jesse Jackson coined the term. The US government has trouble defining the term. Since 1977, in an attempt to keep up with changing social opinion, the United States government has officially classified black people (revised to black or African American in 1997) as "having origins in any of the black racial groups of Africa." Other federal offices, such as the U.S. Census Bureau, adhere to the Office of Management and Budget standards on race in their data collection and tabulation efforts. In preparation for the 2010 U.S. Census, a marketing and outreach plan called 2010 Census Integrated Communications Campaign Plan (ICC) recognized and defined African Americans as black people born in the United States. From the ICC perspective, African Americans are one of three groups of black people in the United States.

Also remember the first African slaves went to the Caribbean and South America not North America.

The first African slaves in what would become the present day United States of America arrived August 9, 1526 in Winyah Bay, when Lucas Vázquez de Ayllón brought 600 colonists to start a colony. Records say the colonists included enslaved Africans, without saying how many. After a month Ayllón moved the colony to what is now Georgia. They rebelled and lived with indigenous people, destroying the colony in less than 2 months.

You may need to clarify  "American".  Ludwig's answer qualifies if you mean the landmass that was later called North, South, and Central America.

But did you mean the first person of African origin to live in the Americas after the Europeans arrived? Or the first black African to live in the Americas after 1492?

Or the first child of an African born in the Americas? Or the first black child born in the Americas?

Or the first African or black African living or born in a colony that is now part of the United States of America? Or the first African or black African born in the United States of America?

From the archeological evidence gathered both in West Africa and Meso-America, there is reason to believe that the African Negritics who founded or influenced the Olmec civilization came from West Africa. Not only do the colossal Olmec stone heads resemble Black Africans from the Ghana area, but the ancient religious practices of the Olmec priests was similar to that of the West Africans, which included shamanism, the study of the Venus complex which was part of the traditions of the Olmecs as well as the Ono and Dogon People of West Africa. The language connection is of significant importance, since it has been found out through decipherment of the Olmec script, that the ancient Olmecs spoke the Mende language and wrote in the Mend script, which is still used in parts of West Africa and the Sahara to this day.