Strangely, Irish, Indian, Pakistani, Russian, Australian, New Zealander and Chinese characters are rarely shown drinking tea on American series, but it's just as popular in these countries, especially in China, where Camellia sinensis
(the tea plant) was originally discovered and cultivated (2000 BC), and is the tea-drinking capital of the world (unless it's Turkey, which is ironically associated with coffee
even though tea is more popular). Even in certain regions
of the United States, tea is quite popular, but it's of the iced, sweet variety. The ritual (and we do mean "ritual": Japanese tea ceremonies in particular are very elaborate and missing a step is a cause for great
offense) is different in these countries: tea is generally drunk without
milk in the rest of the world, due to the fact that most non-European populations tends to be more prone to lactose intolerance. The British tradition of adding milk to tea is likely due to British tea being "black", high in tannins and therefore very astringent, an effect which the addition of milk counteracts to some extent. It may also stem from the days when tea was an expensive luxury and milk was cheap, so lower and middle class Brits used milk to stretch the drink. There's an occasional debate about whether or not the milk should be added first, with purists arguing that the milk should be added after the tea has had time to cool so the boiling water doesn't break down the milk fats.