merica vs US

merica and US both are nouns.

Word	Noun	Adjective	Verb	Adverb
merica	Yes	No	No	No
US	Yes	No	No	No

As nouns, US is a hypernym of merica; that is, US is a word with a broader meaning than merica:

merica: A pejorative term for the United States
US: North American republic containing 50 states - 48 conterminous states in North America plus Alaska in northwest North America and the Hawaiian Islands in the Pacific Ocean; achieved independence in 1776

Other hypernyms of merica include America, the States, U.S., U.S.A., United States, United States of America, USA.

merica (noun)	US (noun)
A pejorative term for the United States	North American republic containing 50 states - 48 conterminous states in North America plus Alaska in northwest North America and the Hawaiian Islands in the Pacific Ocean; achieved independence in 1776