Did the fact that sharecroppers usually couldn't read and/or write have and effect on their situation? How?

In a sense yes. To be sharecropper didn't really require anything but knowledge of farming and muscles, but if you were trying to make life for yourself other than farming, education was a big necessity. At the time, blacks were the main group of people who "crop-shared" because at the time, they had just been freed of slavery, and slaves were not allowed an education. Also most schools at the time did not allow blacks in whites schools, and educated black people to start schools were few and far in between.