An American Tail

In Shostka in 1885, the Mousekewitzes, a Russo-Jewish family of mice who live with a human family named Moskowitz, are having a celebration of Hanukkah where the father gives his hat to his 7-year-old son, Fievel, and tells about the United States, a country where there are no cats. The celebration is interrupted when a group of Cossacks ride through the village square in an anti-Jewish arson attack and their cats likewise attack the village mice. The home of the Moskowitz and Mousekewitze families is destroyed.

In Hamburg, the Mousekewitzes board a tramp steamer headed for New York City. During a thunderstorm on their journey, Fievel suddenly finds himself separated from his family and washed overboard. Thinking that he has died, they proceed to the city as planned, though they become depressed at his loss. Read more on Wikipedia.