Final answer:
David Walker's claim asserts the significant contributions of African Americans to the United States and challenges the notion of white ownership. He emphasizes the sacrifices made by the black population in building and enriching the country.
Step-by-step explanation:
David Walker's claim that 'America is more our country than it is the whites' means that he believed African Americans had contributed significantly to the development and prosperity of the United States through their suffering and sacrifices. He believed that the black population had shed blood and tears to build and enrich the country. Walker's statement was a powerful assertion of African American ownership and entitlement to the United States, challenging the notion that it solely belonged to white Americans.