"Homelessness then, in Australia, is more than lacking a roof over your head, it is also the absence of those features associated with “home”: permanence, security, and the freedom to come and go."
"If the world were to accept Australia’s definition and include everyone with inadequate shelter, the number would exceed 1.6 billion – roughly 20 percent of the population. Also excluded from official figures are the world’s 65 million displaced refugees in temporary accommodation."
merely being mobile or moving a lot is not likely enough to make you considered homeless by the Australian definition.
however, if you were mobile BECAUSE you were unable to obtain a secure residence and tenureship, or the residences you inhabited were of such a low standard that they didn't meet community standards for acceptable habitation, then you probably would.
I'm struggling to remember, but there would likely be a means/ intention component as well: so FIFO workers, mobile executives are not homeless, but couch surfing students or young people may very well be (even if they spent recent time sleeping under a roof). people camping (or glamping), grey nomads, for example, aren't considered homeless.
that being said, even if these people were counted, it's more of an argument that Australian official numbers should be even lower (though i'd recommend most people to focus of the primary/ first level homeless count for the common "popular" view of homelessness if we're going to reduce a complex phenomenon to a simple digestible stat: but it has the downside that people can then tend to misinterpret low homelessness for other arguments: say, how much poverty there is or how much social housing we need.
The obvious alternative explanation is that Americans might simply be less tolerant of measures to decrease the visibility of homeless.
The basic issue is that Australia naive measurements and numbers carry a three tier definition of homelessness: at the lowest level you have what we call "sleeping rough" which is probably the concept closest to what most people and Americans think of as "homeless". But the Australian definition also includes the likes of insecure accommodation and inappropriate accommodation: couch surfers, people living in accommodation with inadequate living conditions, people sleeping in their cars, in socially provisioned homeless accommodation and emergency/crisis accommodation (domestic violence, youth, men and aged issues were the traditional breakdown of most services in my day).
To compare between the two nations from official sources you have to bring them back onto a somewhat comparable basis.
Another source include homeless service provisions, but last time I looked at those they didn't always tend to be on a individual natural person basis.
lastly, homeless service provision, with a few caveats, is one of the only things that might locally and empirically show behaviours of what economists call a "giffen good". And, somewhat paradoxically, provision of homeless services can, to a point, increase the percieved systemic demand for homeless services. increased supply can also create more (real and percieved) demand. the relationship these complexities have with trying to measure homelessness is tricky to say the least...
Australia does provide public housing, but I'll take a stab and say it's cut back from its peak amount.
When you travel through California (and the US in general), i'd estimate homelessness and poverty to be at least an order of magnitude worse in the US (I want to hesitate to say two orders of magnitude worse) compared to anything I see at home. Clearly there's something about society and/or the structure of social safety nets that has a real and measurable effect on poverty and homelessness overall.
/ before someone jumps onto Google to try to disprove me: I've been to both countries (several times in fact), and worked with both homelessness and official national statistics. One of the things internet pundits misunderstand is the definition and measures of homelessness/poverty between the two countries: I think my estimate is pretty fair napkin math, it might be a 4 or 5 multiple instead, but I think we're quibbling by that point.