China in the 17th century was the late Ming dynasty and the early Qing dynasty. The Ming dynasty was an isolationist government - they periodically banned private shipping, burned privately owned ships, and drove the population away from the coastline. Essentially, they disliked foreigners and their influences (including trade) and weren't afraid to show it. The Qing dynasty continued these types of policies as well.
Japan in the 17th century was also isolationist. In the mid 17th century, a policy called the kaikin was enforced. This prohibited foreign contact with most outside countries (however some trade and diplomatic relationships were still carried out). This was only removed in the mid 19th century.
North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere; it is also considered by some to be a northern subcontinent of the Americas
Generally speaking, yes, it is true that a person will understand the compressed language of a poem better if she brings her knowledge of areas such as history and mythology to that poem, since this will help her understand potential "hidden" themes.
