There are African-American members in the Amish Church. Most Amish church members, however, would identify as Caucasian or white. The majority of Amish immigrated to the United States from Europe.
It is very rare for someone to join the Amish Church, and even more rare for an African American to do so. A seeker wanting to convert would need to learn Pennsylvania Dutch, which is the main language spoken by the Amish. They would also commit to following the Ordnung, which are the strict rules that the Amish live by, which include not using modern electricity or machines. The Amish also sometimes foster or adopt children of different races, who might then choose to become Amish as adults.