How to say "USA" in Korean

Why do Koreans call USA "Miguk"?
It is actually from Chinese.
Chinese people call America(USA) MEIguo.

MEI is probably from ME in aMErica.
When ancient chinese met Americans, probably the ME sound stood up to them.
Guo is nation.

They write Meiguo in this way, 美国. (If you translate this directly, it means "Beautiful Country.")
We read this Chinese characters in Korean way. And that is Miguk.

This is how you say, "I am American."

Are you from Miguk? 
Then, like this post! :) lol.