Tea grows in tropical and subtropical areas. In the warmest regions of the world, such as Taiwan, it can be grown at a rather high altitude, whereas in colder climates, such as the east coast of the U.S., it can only be grown at low altitudes in sheltered areas, such as coastal south carolina.
Tea is mostly grown in countries in South and Southeast Asia including China, India, Japan, Sri Lanka, Indonesia, and the like, and also in Africa, such as Kenya, Malawi, and Tanzania, and in South America in Argentina and nearby countries. It is grown in Turkey and Iran (the humid, mild, coastal areas) as well. Georgia (the country) also grows tea in its mildest, coastal areas.
Tea likes humidity; it can handle some cold, such as a light frost, but can also be grown in purely tropical areas. It doesn't have much in the way of soil requirements--it can even grow in areas with very poor soil, even on barren rocks and cliffs.
Only small amounts are grown in the US.