This paper examines how British imperialism brought about transnationally related changes in the trade and production of Asian tea as well as tea culture and politics of North America between the mid-seventeenth and the mid-twentieth century. These changes reflected a growing theme of globalization in the local political and social histories of the two continents, which developed as a result of Britain's imperialist policy of utilizing Asian-grown tea to finance the British Empire, especially its colonial rule in Asia and North America. Westernized consumption of Asian black tea with sugar was developed in Britain after the mid-seventeenth century, and was exported to its settler colonies, including those in North America. It was not only the domestic consumption of Chinese tea in Britain but also its popularity in the British colonies which led to the dramatic increase of tea importation from China and to the Anglo-Chinese Opium War (1839-1842). Such demand for the Asian herb further led to its plantation in India and Ceylon under British control from the mid-nineteenth century. British imperialism and tea consumption also influenced tea culture in colonial New England, and especially, heavy taxation on the import and retail of Chinese tea sparked the American Revolution. Nonetheless, British-style tea culture still left a permanent legacy in the United States in the post-revolutionary era. By contrast, in Canada, the British-style tea culture, especially Britain's new policy toward reciprocal trade benefits with its colonies from the late eighteenth century, resulted in expanding revenues for colonial governments. The popularity of British tea culture in Canada and other remaining colonies not only enhanced colonists' identity with Britain and ensured its imperialist cultural hegemony overseas but also helped the British-controlled tea product in India and Ceylon to prevail over the previously prevalent Chinese tea in the international market by the early twentieth century.