Aside from America, the nations of Liberia and Canada, the Australian territory of Norfolk Island and the unincorporated American territory of Puerto Rico are known to celebrate Thanksgiving as a national holiday every year. Canada celebrates its Thanksgiving in October, Liberia commemorates this occasion in early November, and Puerto Rico celebrates at the same time as the continental United States.
Though Americans may tend to think of Canada as simply being neighbors to the north, their Thanksgiving celebration actually predates America's by almost 100 years. However, this doesn't mean that one celebration was inspired by another. It's simply a case of two popular harvest festivals being celebrated at the same time of year under the same name.