The use of the words "would" and "could," alongside specific punctuation choices, can convey a sense of uncertainty, possibility, and hypothetical situations. In the context of discussing racial equality in the United States after the Civil War, these words can suggest that achieving equality was seen as uncertain or dependent on various conditions.
Therefore, the most fitting effect would be:
It builds the uncertainty that all Americans faced toward many elements of society after the Civil War.
The focus on the hypothetical nature of the statements can highlight the struggles and challenges in the era, reflecting a pervasive doubt about the future of racial equality.