It is really not that complicated. The fact that is a such a large number of people who have absolutely nothing, no property. nothing. It pulls average down far below what you would consider "middle class", thus statements about someone having a $300,000 or $500,000 property, being "middle class" comes off as out of touch.
Well, my main point was that everywhere outside the US 'middle class' means the upper strata of society.
I don't think that's true in the developed world. If you're talking about the Chinese middle class or the Brazilian middle class, sure, you're talking about the 80th to 99th percentile incomes of the country, but I don't think that's true of Germany or France or Canada or Japan. (Britain I'll leave aside since class in Britain is less about income/wealth than other things.) The definition is perhaps not *quite* as expansive as in the US (where the real problem is that everyone self-identifies as middle class rather than that people really mean 90% of society when they use the term "middle class"), but it at least drops to the 40th percentile or so of income.