The term murica is the way how many people with extremely thick, American accents, pronounce America. The term is used to denote extreme, extreme nationalism and patriotism, but not necessarily facism. It is generally seen as a derogatory yet humorous way to describe most Americans: fat, lazy, gunwielding, war loving, horse riding, saloon fighting, beer drinking, sex wanting or etc.
according to knowyourmeme, murica originated from a post in 2003, but then re-appeared a year later from the red states who voted for George Bushs re-election.