What is the punch line of this American joke?

The female teacher asked in class, "Give me freedom or let me die." Who said this sentence? Please raise your hand if you know. After a while, someone answered in unskilled English: "1775, Butrick Henry said." "Yes, classmate. The answer just now was Japanese students. You grew up in the United States and can't answer, but students from distant Japan can answer, how pitiful! " There was a strange cry in the classroom, "Kill the Japanese!" .

The female teacher blushed with anger. "Who? Who said that? ! "After a short silence, someone in the corner of the classroom replied," 1945, said by President Truman. "

Maybe the joke is that the teacher just wants to ask, "Kill the Japanese!" Which classmate said that, but the student thought the teacher was asking "kill the Japanese!" " "Which historical celebrity said that, and then answered" 1945, President Truman said that. "

This joke is not funny at all = = The people who laugh laugh so low.