Jokes caused by differences between British English and American English

A man who just learned a foreign language was walking in the street that day. He accidentally stepped on a foreigner's foot. The man quickly said, "I'm sorry." The foreigner also said politely, "I'm sorry, too." Hearing this, the man quickly said, "I'm sorry, three." The foreigner was stupid and asked, "What are you sorry for?" The man said helplessly, "I'm sorry."