90% sure that is a rhetorical statement but I am going to try and answer it anyway.

It's the same reason why a vaccume cleaner is called a hoover. A hoover is a vaccume cleaner. A vaccume cleaner is not always a hoover, yet loads of people call the floor sucker hoover no matter if the brand is a Hoover or not.

Nobody really care if someone says "I am getting the hoover" and pulls out a Dyson. Everyone was expecting some kind of floor sucker with maybe a select few expecting an actual Hoover.

You can ignore what the official name of the USA is. People already do that. They the USA America all the time already. AUS will be a little confusing at the start as many associate that with Australia but get enough people together to call the USA, the AUS instead and it's not going to be wrong.

A good example of people not using the correct name of a country is the UK ain't nobody using the full name the United Kingdom of Great Britain and Northern Ireland are they? The initialism is wrong too it should be UKGBNI