The US apparently has about half the median wealth of many European countries, although notably not Germany, which is comparable to the US on this metric.
But I'm not sure how meaningful this is or what factors might be affecting the numbers. (And I'm not even exactly sure what's being measured.)
For example, say your house went from 400k-500k in a year. For it to be 500k you still have to find a seller. Yes, there's a degree of paper value there however it's paper value only because other properties are selling for that. If you were to somehow remove property from being bought and sold, the money would just go into other investments. There is no way that 'most' of that wealth is wealth on paper in the form of property.
The reality is that Australian wages are very high comparitively. Australia is a wealthy nation.
What is there about the German standard of living for typical citizens that compares unfavorably to the US? How can this be measured? No single number works, but I would suggest looking at medians ahead of means.