Whether an Australian is poor by (say) a Burkinabe's standards is immaterial, since they have to live in a high-cost of living country (Australia) not in Burkina Faso.
This is IMO a naive and fallacious argument. Charities are largely localised in their activities, so charities serving wealthy neighbourhoods will be far better funded than those serving poor areas, since the wealthy have far more incentive to fund charities that serve their interests than charities that don't. Charities have a limited capacity to serve poorer areas for that reason. If you're a needy person in a remote area? You're largely on your own.
Also, if the wealthy dislike paying tax, why would they like funding charities that don't serve their interests?
Countries with high inequality (USA, Brazil, Mexico, South Africa) tend to suffer from crime, political corruption and social dysfunction. Not to mention that for a first world country, the US has utterly appalling infant mortality/drug use/literacy rates (as many as 43% of Americans are functionally illiterate).
Unless that's the sort of society you want to live in, then enforcing equality is important.
Also, I don't understand how enforcing equality discourages people from taking personal responsibility? Is a lack of personal responsibility solely responsible for the ills that the lower classes suffer from? I doubt it very much.
Economic freedom and 'taxation' aren't the same thing. Our top marginal tax rate is on paper slightly lower; our corporate tax rate is generally higher.
I would contend that the USA is really 'pro-socialism for the wealthy'.