>Even so, they are united States (as opposed to, say, Australia where the so-called "states" are for all intents and purposes merely administrative subdivisions of the continent, and could be remade by passing a law in the federal parliament)

I don't think this is accurate. Prior to federation there were no Australian states, there were 6 independent colonies.

The status of the states are part of the Australian Constitution to make changes (such as creating a new state) would require amending the constitution and thus a referendum.

The Australian States have quite a bit of power its one of the "challenges" we have here because of the way our constitution is written in order for a referendum to pass it requires a double majority you need an overall majority as well as a majority in a majority of states (i.e 4 out of 6 states must also have majority support) this is one of the reasons constitutional amendments are so difficult and rarely pass here.

Similar thing with our senate (Upper house) each state has equal representation in the senate so both Tasmania and New South Wales have 12 Senators despite much smaller population in Tas. This is in contrast to House of Representatives (our lower house) is not equal (there are 5 seats in Tasmania vs 47 in NSW) this has a lot of implications in our political process.

As far as people not feeling loyalty to their state that's mostly true but there is still a lot of friendly (or not so friendly rivalry) especially in sporting events.