The line you’re referring to I believe is from the poem, “Oh, Captain! My Captain!”
The lines refers to the fact that the North has won the Civil War (in the United States).
the Miranda rights. this is why the police read you your Miranda rights when you are arrested.
It was made law that a police officer has to read you your rights when you are arrested because a guy with the last name of Miranda didn't know that he had the right to remain silent when he was taken into custody for an awful crime (I think it was either abduction or rape).He told the police everything because he didn't know he had the right to remain silent. He brought his case to court and won the new law was named the Miranda rights after his last name.
McKay personifies America as a woman who feeds him "bread and bitterness" and who sinks her "tiger's tooth" into his throat. By using the pronouns she and her to refer to America, McKay turns the concept of a country into a person who can cause the narrator harm even while he loves her. The effect of this personification turns the relationship between the narrator and his country into a more personal relationship, full of the conflicting emotions that come along with loving a person.