Quora is one of the best social networks in terms of questions and answers. Needless to say, there are numerous questions and answers about the English language. This is a particularly good example:

QUESTION

Why can you say “in the Ukraine” but not “in the Germany”?

ANSWER

Because Ukraine used to be a nonsovereign region of a state/empire, and has only recently ceased to be that. There are plenty of countries for which English speakers do use a definite article: all countries with a common noun as part of their name, e.g. “The United States of America,” “The United Kingdom,” “The People’s Republic of China.”
There are also countries and places without common nouns that none the less require a definite article: “The Netherlands”, “The Hague”, “the Gambia”. Regions tend to also receive definite articles: “the Amazon”, “the Upper Nile”, “the Rockies.” In the 18th and 19th centuries, before German and Italian unification, English speakers regularly referred to “the Germanies” and “the Italies.”