Accents are what you're talking about here. The game remains utterly unchanged at the fundamental level: the rules. None of these countries have influence the game beyond a merely expression within its static architecture. This is quite different to the three other football codes we play, whose fundament DNA has been altered by our influence.
Why you can't grasp this incredibly simply point is truly bewildering.
Point me to a country which has cities analogous to Sydney and Melbourne where there are four codes of football each with top level professional teams. England has a shitload of soccer in London, plus Union and a token failed League team, which it can't support despite having the population of Australia. Basically the city is owned by soccer though, and London would be the closest to us in terms of football code representation.
Yes, no economic benefits:
http://www.cbc.ca/news/business/world-cup-financial-gains-rarely-materialize-for-host-1.2671024
For the record, the AFL have been pretty successful at getting their stadium strategy in place, which means its more about the lobbying capacity of the sport, something which the NRL is now getting much better at, with news that Smith has convinced the NSW government upgrade several grounds.
So no, we don't need the corrupt FIFA scum coming in here and forcing shit down our throats, whilst stealing all our money just to get a decent stadium. Being involved with such utter human filth frankly is unnecessary and wouldn't even be worth it if it was.