I would guess that Oz got more misfits, prisoners and exiles than the US did, but over a shorter span, albeit at a faster pace than the US in the colonial period.
I think the socialistic tendencies in their polity started about the same time they did in all the 'White Dominions' of the British Empire.
Not sure of exact dates but Canada, Australia and New Zealand all moved towards self government and some replication of UK politics around the same time, say 1880s on (I know, confederation is 1870 in Canada), with divions into Liberals (whatever their local name), Labor and United Empire Loyalist types (traditionalists, conservatives, imperialists).
You can't have a lot of confidence in the strength of your own culture if you're that terrified the "forners" are gonna take it away from you. I doubt this was the authors intent, but the whole article screams "fear"