The Article "The"

This is a simple little mistake I have been noticing students committing in a variety of essays lately. The article "the" should be used in front of a specific or particular noun. But, when we are dealing with geography there are some unique rules to follow.

The key rule I want to emphasize is that "the" should not be placed in front of countries or cities.

Incorrect example: "In the America there is an obesity problem."
Correct example: "In America there is an obesity problem."

Now, it gets even more complicated because if you are talking about The United States of America, then yes, go ahead and write "the U.S.", but that is a unique case. I don't want to see "the Korea", or "the Japan" in essays in the future.