Answer:
De Crevecoeur was not thinking of enslaved Africans when he made the statement given in the question, he was talking about the people that have settled in the America at that time.
Step-by-step explanation:
De Crevecoeur was a French immigrant, who lived in North America. In 1782, he wrote a series of essays, which he titled 'Letters from an American farmer'. In the essay, De-Crevecouer said that an American was a person who leaves behind his custom and manners and adopt new ones to develop this new land.
The new land that De-Crevecour was refering to was the United States of America, which just become newly independent at that time. This essay gave the Americans the idea that a new nation based on shared equality can be created. People, who settled at United state at that time came from different nationalities and uphold different cultures. At that time, De-Crevecour was expressing a desire that all the people from diverse cultural backgrounds in America should work together to develop the land of America. That desire actually come to pass although De-Crevecouer was no longer alive then.