Population size accounts for most of it. The population of Florida is roughly close to Australia and the output is roughly the same. China is an outlier but that is because it’s only recently (few decades) moved from third world economic status to a powerhouse. GDP per capita could help explain more, as would a debt chart overlayed on this one (and a debt per capita on the gdp per capita chart).

Population saves up to try to move to where the opportunities are. Australia is almost exactly the same size as the continental United States, with a similar endowment of minerals. But our government regulates everything the way yours regulates healthcare. Professional wages in the US nearly double ours as a result.