Is the name of the country south of the United States spelled México or Méjico? Which is the official name of the country in English and Spanish? When is each version used?
You can see from the official Mexican seal, that the official, modern name is spelled with an
Google ngrams also shows that, since roughly the mid 1850s, México has been the preferred spelling:
The official name is Estados Unidos Mexicanos or Mexican United States and it is only used in government official documents.
The United States was added in part inspired by our northern neighbors, United States of America.
In normal conversation we use only México. There are some efforts by some politicians to change the official name to just México.