Americans are traditionalists. The reason Americans call football “soccer” is because “soccer” is what the Irish and British immigrants who came to America called the game.
The term “soccer” is an acronym, but to understand the acronym, you must know the history of the game.
GAMES, FOOTBALL & SOCCER
In the UK, during the 1800’s, there were essentially 2 types of games – those played on horseback (by the rich people), and those played on foot, by everyone else. Any games played on foot, with a ball, were called – you guessed it – “football“.
In it’s infancy, football was mostly played in school yards by boys (girls absolutely did NOT play football) with rules that varied day-to-day and game to game. The simplest of these games usually involved a goal or end-line on either end of the field, with the boys using any means necessary to get the ball down to the other end.
As games got more organized, someone got the idea to create a school league, and schools began playing each other.
SCHOOL BOYS AND THEIR GAMES
Since each school had their own set of rules, there had to be a clear understanding of the rules they would abide by, when playing at one another’s fields. It was most common to show up at a school, and play by the rules of the school. As football became more popular, the games continued to evolve and a few games of football began to stand on their own. Ruggers, Society Rules and Gaelic football were the most common types of football played.
As time went on, Ruggers came to be know as Rugby, and Society Rules came to be called by the acronym SOCR (SOCiEtyRules), or “soccer”.
In 1863, a fellow named Ebenezer Cobb Morley drew up some “official” rules for the “society rules” game, and presented them to the newly formed Football Association (the FA). These official “Association rules” essentially changed the identification of “society rules football” to be “Association Rules Football”.
From that day on, when anyone called the game “socr” or “soccer”, they were chastised, ridiculed and educated: “It’s FOOTBALL!” It still happens today.
Immigrants to the United States from the United Kingdom (mostly Ireland), who were not educated to the rulings of the newly formed Football Association, called the game “soccer” in their new country. Immigrants who brought ruggers and other football games over to the New World AFTER the forming of the FA, in the early 1900’s, developed their own “American” football.
Like in the UK and Australia, the national brand of football became synonymous with the term, and other brands of football were called by their regionally established names – like the old UK’s “society rules” football, or “soccer“.
So, Americans call soccer “soccer“, because the English called it “soccer” FIRST.