A recent io9 article about, of all things, the 1997 film Starship Troopers reminded us that the diverse Gizmodo Media commenting and writing communities have different opinions on how to define football. Obviously the solution here is for someone on the ODeck to claim they know everything.
The sources of the problem
As was mentioned in this article’s prequel, this diversity of opinion exists for three primary reasons:
1 In various Anglophone countries, several (three? four? five?) different sports of football were codified out of proto-football in the 19th century.
2 Every one of these different sports is very sure that they created football first or created the best version of football and that other version of football is a secondary or inferior product.
3 Anglophones seem to be really unwilling to acknowledge that the word football is capable of meaning multiple things.
Personal anecdote time
As an Anglophone of North American origin and residence the earliest football team that my brain was aware of was this one, shown in video format:
As you can tell they seem to be proficient in seven musical instruments (electric guitar, electric bass guitar, saxophone, cowbell, keyboard(s), two kinds of drums) and I think that has something to do with how they play football. Unfortunately the video cuts out before they score any goals so it doesn’t completely illustrate how this version of football is played.
Not long after my introduction to that football team I was also exposed to knowledge of an entirely different football team, this one:
But because I was in the USA I was told that this second team played a different sport: they played soccer. It’s right there in the teams’ respective leagues; the Chicago Bears play in the National Football League and the Chicago Sting played in the North American Soccer League and the Major Indoor Soccer League. Obviously they can’t both play football: note how in the photograph no one is on the drums.
Words are congruent upon species
Why couldn’t both teams be called football teams? It’s for the very simple reason that words in a written and/or spoken language are functionally similar to biological species. There are plenty of good examples and “football” in particular is a fantastic example of how words evolve and adapt; it had an ancestral form which was spread into several different environments (different schools in the UK and different continents of Anglophone speakers) and as the gene (meme) pool spread beyond a cohesion point, word speciation occurred and several new species of football all diverged. These species are kept distinct from one another by the introduction of barriers (different rules of play), strengthening the mimetic divides between them. Ecological conflict occurs when the species are brought back into contact with one another; in an environment there is a singular niche for “football”, and only one species of football can occupy that niche.
This niche occupation is also part of why it is so difficult to change the name, change a very prominent species characteristic, of something which occupies that niche. Humans as individuals require mental processing time to internally redefine a word; we often learn one meaning of a word at a young age and then require effort to discard that meaning. Asking a society to commit this same definition change is a monumentally more difficult task because naming conventions have long-standing sociocultural pillars. The different species of football have been distinct from one another for over a century; each has a heck of a lot of cultural and social weight attached to it.
Linnean nomenclatural suggestions...
In biological nomenclature the solution to this dilemma of “multiple things using the same name” was decided upon in the 1750s: every biological category would have its own name and that name would be primarily based in dead languages so that their meaning would not dramatically shift over the course of human history. Further regulations were added in the late 19th century so that different branches of biological nomenclature had different governing bodies over names. For the most part nothing like this happened in sport; particular sports are very interested in defining and regulating themselves but there are few organizations which seek to define multiple sports.
But there are some, and two of the most prominent ones do not follow US naming conventions.
The Olympics has two kinds of football games at an international level of competition. It refers to association football as football and it refers to rugby football as rugby. No gridiron football has appeared at the Olympics except as a demonstration game.
SportAccord is an organization that tries to coordinate as many international sport leagues as it can. It refers to association football as football (the Fédération Internationale de Football Association joined it in 1970) and it refers to gridiron football as American football (the International Federation of American Football joined in 2005).
And in terms of international languages, well, Esperanto is one and it distinguishes futbalo (association football) as distinct from usona futbalo (gridiron football).
...and their limitations
So the Anglophone world in general has defined football as not what most Americans think of as football, and gridiron football often has to distinguish itself as American football in order to acquire international fans. That’s the entire point of the IFAF, it seeks to promote gridiron football to audiences outside of the US and since the word “football” is already taken, it has to sell its product as American football.
But none of that matters in the US, because the US is unlikely to ever add “gridiron” or “American” to the name of its football leagues. It’s assumed within the US that any reference to “football” is to gridiron football, and that’s just the way that US-English works.
This same basic point was reached in the prequel article; various sport organizations in the US decided to call gridiron football just simply football even after football had already been defined in the English language. That’s why this word conflict exists in the early 21st century; US- and UK-English have competing definitions, neither is willing to admit defeat, and since both contribute large amounts of Internet and other popular cultural media content, people who are Anglophones in other countries are exposed to both definitions.
Starship Troopers has an arena gridiron football game between two Argentinian high school teams because it happens in a future in which US-English took over the world.
And/or because its script was written in the US by a US citizen.