Both "N. Korea" and "S. Korea" do not use those names for their countries.
The Spanish do not call their country "Spain".
Many people around the world do not call the US by the same name we do either.
We all do not even call the world oceans by the same names.
Picking a name for a country or region that is different than what that contry calls itself is common and normal. Heck few people in the world have the ability to read and pronoucnce all the country names in the original languages.
In this case, it looks like a classic situation of giving a pronounceable name to a country so that English speakers how what/where it is. It is not like they grabbed it out of nowhere.
It is NOT that the US "renamed" something and that becomes the permanant new name anymore than we would expect to rename the US when other cultures call it by a different name that suits their language.
Because lifedeath did not explain, FYROM stands for Former Yugoslave Republic of Macedonia. She fully admits that has been the commonly used name for that region in current times and she seems to accept that name.
How is it wrong for people to shorten it and call it "Republic of Macedonia"? That is NOT a new name and was not given by the US if her post is accurate.
EDIT:
I have been looking up a bit more on the issue.
Seems the US and most international organizations still call it FYROM. The term Republic of Macedonia seems to mostly be used by Turkey.
Checking the CIA World Factbook for 2004 backs this up. The US still calls it FYROM.
From fact-index.com
"The state's name remains a source of local and international controversy. Internationally, the republic is known exclusively as FYROM in political and cultural organizations, notably the United Nations, the European Union, the European Broadcasting Union, NATO and the International Olympic Committee among others. Most diplomats are accredited to the republic using the FYROM designation. The usage of each name remains controversial to supporters of the other. A few countries, notably Turkey, refer to the state as the Republic of Macedonia, rather than FYROM. A permanent agreement on how the Macedonian republic should be referred to internationally has not yet been reached. "
Checking the US State Department web site show that according to official US policy there is NO short form of FYROM.
LINK HERE