Why do you say the US or the United Kingdom and not the India?

Answer 1

You would not say "the America", and you would not say "the China". When you are talking about a country (not a nation) or a continent, it will usually be without the definite article (the). Many nations, on the other hand have official names that say something about them politically, or about how their government is organized. So you could say "I am visiting China next year" or you could say " I am going to the People's Republic of China". By the way, "The Republic of China" refers to Taiwan, and not mainland China.

There are a few countries, though, that are often referred to with "the" in the name; for example, the Ukraine, the Gambia, the Congo, and the Lebanon.